Abstract: Cultured marine diatom, Rhizosolenia alata (Brightwell) were freeze dried and extracted with solvents such as acetone, chloroform, chloroform: methanol (1:1), methanol: distilled water (4:1) and distilled water. The extracts were screened against 7 human pathogenic bacteria for their antibacterial activity. All the organic solvents showed activity against all the pathogens tested with a maximum activity in chloroform against Proteus vulgaris and minimum in chloroform: methanol against Staphylococcus aureus. However, there was no activity in distilled water extracts against all the pathogens tested.