Organization, storage and providing access to information are amongst the key tasks of information specialists. Systematic and reliable information organization is especially important today, when we are surrounded by vast amounts of data, making it increasingly difficult to identify high-quality scientific information. This dissertation examines the subject approach to information in a sample of selected Croatian biomedical scientific journals and monographs. Background: The introduction of this dissertation describes the theoretical bases and different systems of information organization, with emphasis on development, structure and the importance of thesauri, and methods for information organization in contemporary networked environments. Special attention is paid to Medical Subject Headings (MeSH), a thesaurus used for subject cataloguing, indexing and searching of biomedical literature, and MEDLINE, one of the largest international biomedical bibliographic databases; both of which are considered credible information sources in the worldwide scientific community. The remainder of the introduction includes a short overview of medical publishing in Croatia, as well as the practice of subject cataloguing in the Central Medical Library at the University of Zagreb Medical School and the Croatian National and University Library. A review of available information sources found a small number of papers concerning this topic, and showed that Croatian information sources have not been involved in similar research; so this investigation reveals new information about the subject analysis of medical publications in Croatia. Objectives: Similarities and differences in subject approach to information between authors and information specialists were investigated through an analysis of key words given by the authors of articles in Croatian medical journals. Author keywords were compared with terminology in MeSH and with MeSH descriptors assigned to respective articles by information specialists in the bibliographic database MEDLINE/PubMed. The practices of Croatian information specialists were shown by comparing the subject cataloguing of medical books in two Croatian libraries. Hypothesis: 1. A certain number of free-formed author keywords will have no equivalents in the MeSH thesaurus. 2. Keywords submitted by authors will not always correspond to the descriptors in the bibliographic database MEDLINE/PubMed. 3. The correspondence will be greater in the articles in which authors used MeSH. 4. Subject indexing in two libraries will vary, but the degree of correspondence will be greater than in point 1 and 2. Materials and methods: This study was performed using 161 articles from three selected Croatian medical journals indexed in MEDLINE, and 46 bibliographic records of medical books found in Central Medical Library and National and University Library. The methods used in the investigation included: counting, analysis, comparative methods and methods of descriptive statistics. Results and discussion: The results revealed both considerable similarities and differences in subject approach to information between authors and information specialists and between information specialists themselves. Regarding the choice of terminology, 65% of the free-formed author keywords were related to descriptors from the MeSH thesaurus, almost half of which were corresponding descriptors (32%), and additional 24% were corresponding MeSH entry terms. This suggests that most author keywords could be replaced by MeSH descriptors if only the editors in medical journals insisted. The analysis of subject approach to information showed that 70% of the author assigned keywords were related to the descriptors in MEDLINE (34% corresponding descriptors, 8% entry terms). These results are somewhat higher than those found in similar international studies. Only 36% of all descriptors from MEDLINE were connected to author keywords, but the main subjects in MEDLINE showed greater correspondence (77%). The results varied between selected journals, showing the highest consistency in Lijecnicki vjesnik – the only journal where the authors used MeSH, and the editors corrected the author assigned keywords. Regarding subject headings, 65% of the ones from the National and University Library corresponded with MeSH descriptors, and an additional 11% corresponded with MeSH entry terms. The consistency of indexing between the two libraries, calculated using Hooper’s formula, was 34%. Conclusion: The results of the investigation confirmed all initial hypotheses and indicated the need for increased cooperation between the authors, creators and users of the information, and the information specialists. Since MeSH is an international standard for subject indexing in biomedicine, authors should learn more about it. Using MeSH descriptors in the writing and subject indexing of their papers could increase their international visibility. The editorial boards of scientific journals should also use a more systematic approach regarding author keywords, prescribing the MeSH thesaurus as a mandatory source of terminology, and controlling the consistency of its use. On the other hand, information professionals should be more open to user contributions in the construction and modernization information organization systems. They could include author and user terms in the existing controlled vocabularies as additional entry terms or as new descriptors, and enable searching of bibliographic databases using author keywords. In order to ensure a more consistent subject approach to biomedical information, libraries should use the MeSH thesaurus either in its complete form, or as a source of terms for the construction of their own subject headings lists.