Soon after the invention of press, Croats have tried to get into the black art as well. Some were working as printers and some as authors printing their own works. Incunabulas that we are calling Croatian today are the ones that are from Croatian authors regardless of language, the ones that were created in workshops of Croatian printers abroad or in homeland and the ones that were printed in Croatian language. Their copies are preserved in domestic and foreign libraries, and many of them are available in digital format. Most responsible for getting information about Croatian incunabulas are many cultural workers, starting with Ivan Kukuljević Sakcinski, through Josip Badalić and Šime Jurić and many others. Despite their extensive works, there are still questions about Croatian incunabula that have not yet been answered, which has partly been presented in this paper. Project that is just being carried out by the National and University Library should make a major contribution to the Croatian incunabula knowledge base. Works that we currently have preserved have come to us in different ways, and the greatest number of them is being kept in libraries. Seven libraries in city of Zagreb are keeping these preciuos monuments of Croatian culture - incunabulas or early printed books, and four such collections are presented in more detail in this paper. These are the collections of incunabulas of Metropolitan Library, National and University Library, Library of Croatian Academy of Sciences and Arts and City Library from the network of the Zagreb City Libraries.