Culturable aerobic heterotrophic bacterial (CAHB) numbers, total direct counts (TDC), bacterial generic composition and uptake of labelled glucose by natural microbial assemblages were studied from a few selected coastal sites off Tamil Nadu. A high abundance of CAHB and TDC was observed in most locations. Microbial heterotrophic uptake and respiration rates of labelled glucose were high (except off Madras) suggesting a highly active microflora at most of these locations. Many bacterial genera were seen in these sites with a general predominance of Vibrio, Pseudomonas, Aeromonas, Alteromonas and strains of Enterobacteriaceae. Autochthonous microflora along the Tamil Nadu Coast appears to be very active and it is possible to suggest from this study that these communities continue to biotransform organic materials actively at current levels of anthropogenic interactions with these waters.