A mixture of several bacterial metabolites $(Sterodin{circledR})$ was used to study its effect on major immunocytes, in vivo and in vitro. This mixture of bacterial metabolites increased number of macrophages and neutrophils and their phagocytic activity in experimental animals for a transient period. BSA induced antibody production was found to be higher in the drug treated group. These results indicated that the bacterial metabolites probably acted through non-specific defence mechanism against invading organisms and the chance of reinfection was reduced.