The antidiarrhoeal activities of leaf extracts of Ocimum gratissimum were investigated by disc diffusion and tube dilution methods. The extracts were active against Aeromonas sobria, Escherichia coli, Plesiomonas shigelloides, Salmonella typhi, and Shigella dysenteriae. The leaf extracts were most active against S. dysenteriae and least active against S. typhi. The sensitivity of the organisms measured in terms of zone of inhibition ranged from 8.00 to 19.50 mm. The minimum inhibitory concentrations were from 4.00 to 50.00 mg ml-1, while the minimum bactericidal concentration ranged from 8.00 to 62 mg ml-1. The potentials of the leaf extract for the treatment of diarrhoeal diseases is discussed.