Extensive ground based measurements of aerosol Black Carbon (BC) and size segregated aerosol mass concentration (total) were carried out (during August 2000 to October 2001) for the first time at a tropical coastal station, Trivandrum, India. BC depicted diurnal (with a nocturnal peak and mid-after noon low) and seasonal variations (highest during local winter and lowest during monsoon). The diurnal variations were closely associated with the boundary-layer dynamics. Daily mean BC concentration as high as ~6 ¿g m-3 was observed on several occasions. Mass apportionment showed a BC share ranging from ~3% to as high as ~12% to the total aerosol mass, depending on the season. The presence of such large amount of BC over land might influence the regional aerosol forcing.