We calculated the impact factor (IF) of the Croatian Medical Journal (CMJ) for the 1994-2003 period, ie, including the years before its inclusion into the Institute of Scientific Information (ISI) database in 1999. There was a latency period of several years from the inclusion of the Journal in indexing databases to the IF increase. According to the ISI Journal of Citation Report, IF of the CMJ in 2001 and 2002, was 0.43 and 0.71 and journal was ranked 70 and 56, respectively, out of 107 journals under the category "Medicine, general and internal". The analysis of distribution and type of citations that contributed to the IF of the CMJ revealed that its increase mainly resulted from the increase in the number of fully independent citations and author auto-citations in journals other than CMJ. The factors that probably accounted for the IF increase were better international visibility, full-text free-of-charge online availability, and large number of international contributions, especially in some thematic issues.