Thanks to the support of the CBPP-IBP, Washington, the IPF, Zagreb explored the budget transparency of 33 biggest Croatian cities, which resulted in the Croatian Open Budget Index (COLBI) for the year 2010. The goal was to investigate the disclosure of budget information by local units and the openness of local units to the public. Within the project, we: (1) constructed the Questionnaire on the basis of which we calculated the Main COLBI of the disclosure of budget information by local units, the Additional COLBI of the local units' openness to the public and the Total COLBI, as a general measure of local budget transparency; (2) carried out a Survey among the representatives of local information officers (LINFO), local executive bodies (LEXE), local representative bodies (LREP) and local civil society organizations (LCSO) in the observed cities and the Ministry of Finance (MFIN); and (3) engaged a citizen (unacquainted with the budget) to search independently the official websites of these cities.