Abstract: Three antibiotics (RA-1, RA-2 and RA-3) were isolated from the chloroform extract of the fermentation broth of a Penicillium strain of an unidentified species. These compounds exhibited a significant in vitro antibacterial activity against both gram-positive and gram-negative organisms. The MIC values for RA-1, RA-2 and RA-3 were also determined against Bacillus subtilis, Shigella sonnei and Escherichia coli. The chloroform extract also showed strong cytotoxicity in brine shrimp lethality assay.