Croatian Sign Language (HZJ) is the language of the deaf community in the Republic of Croatia. Sign languages have been around as long as the deaf people, but their systematic research did not begin until the middle of the 20th century. The linguistic research of HZJ is in progress, but there are no extensive manuals such as grammars or dictionaries at the moment. The goal of this paper is to collect the HZJ research results published so far in one place. Most of the research papers stem from the Faculty of Education and Rehabilitation Sciences where the Laboratory for Research of Sign Language and Deaf Culture operates. This paper tries to define sign languages, explains the differences and similarities between spoken and signed languages, summarises the known history of sign language development, shows the ways a sign language can be written down, describes HZJ's linguistic units through chapters on phonology, morphology and syntax and reviews the existing HZJ manuals and dictionaries. Besides the above-mentioned, this paper aims to raise awareness on all the issues in HZJ that need further research and on its need for standardization which would greatly ease the communication between HZJ users.