This thesis discusses the state archives of Sisak-Moslavina County. In the Sisak-Moslavina County, there is an archive based in Sisak and a collection centre based in Petrinja. The history of archive's foundation and it is development to this day is presented first. The part of the thesis relating to the history provides information that the archive was established in the City Museum of Sisak as one of the departments before a private building was obtained. Today, the building in which the archive is located has been adapted and reconstructed in order to enlarge the depositories and archival workspace. The second part describes all the work done in the archive. The activities in the archive are divided among five departments, namely: Business administration department, Department for protection of archival materials and records outside the archives, Department for arrangement and description, Department for Users, and the Archival collection centre in Petrinja. The Archival collection centre in Petrinja is considered a department of the State Archives in Sisak and collects archival material from Petrinja. The archive also participates in the organization of professional and scientific conferences, exhibitions and publishing projects that the archive initiate by itself or in cooperation with other institutions. The third part discusses the fact that materials are divided into 15 groups, which are collected since the archives were established in the 1960s. The oldest material in the archive are two charters on nobility from the 17th and 18th centuries. The last part of the paper discusses the fact that some materials that are important for the Sisak-Moslavina County is stored outside of the State Archives in Sisak in other archives or with the creators of archival material. Most of the materials are in the Croatian State Archives in Zagreb.