UNLABELLED Samples of airborne particulate matter were collected at several cities in Indonesia: Bandung, Jakarta, Palangka Raya, Serpong, and Yogyakarta, from January through December 2011. The samples were collected once a week using a Gent stacked filter unit sampler in two size fractions of 2.5 microm (fine, PM2.5) and 2.5 to 10 microm (coarse, PM2.5-10). Black carbon was measured using an EEL smoke stain reflectometer The average of PM2.5 during the sampling period for Bandung, Jakarta, Palangka Raya, Serpong, and Yogyakarta sites was 18.35, 16.50, 7.74, 16.68, and 8.78 microg/m3, respectively. The average of BC for Bandung, Jakarta, Palangka Raya, Serpong and Yogyakarta was 3.05, 3.37, 3.19, 2.51, and 2.20 microg/m3, respectively. The ratio of the 24-hr BC concentration compared to the PM2.5 concentrations showed that BC comprises about 17-45% of the fine particulate matter collected at all sites. The average percentage of BC in PM2.5 concentrations in Bandung, Jakarta, Palangka Raya, Serpong, and Yogyakarta was 18, 22, 45, 17, and 26%, respectively. Bandung and Jakarta compared with Yogyakarta showed higher concentrations of PM2.5 and BC, which indicated pollution occurring in Bandung and Jakarta is more intense than in Yogyakarta, while the maximum of BC concentration and the percentage of BC in PM2.5 in Palangka Raya were 6.04 microg/m3 and 75%, respectively This higher BC concentration than the other cities was due to the forest fires that occurred frequently during the sampling period. The contributions of BC source in these cities were also analyzed to ascertain the local sources of BC. IMPLICATIONS BC in PM2.5 was monitored over the period of January-December 2011 in several big cities in Indonesia to provide quantitative information on BC concentrations and contributions to PM2.5 and for comparison among these cities and with other Asian countries. This study supports the national air quality monitoring projects. The results of black carbon concentrations in these areas indicate source contributions from local sources such as forest fire, biomass burning, and vehicle emissions.