Antibacterial evaluation of the methanolic and petroleum spirit (60-80) oC extracts of the stem-bark of adenium obesum was carried out using agar- well diffusion method. The extracts were tested against some selected standard gram negative bacteria strains–Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC- 25619), Salmonella typhi(ATCC 9184), Neisseria gonorrhea (NCTC 8198), Klebsiella pneumonia(ATCC 15380). Antimicrobial sensitivity test of the extracts at concentration of 4×104 µg/ᴄm3 showed significant zones of inhibition against 80% of the tested organisms. The minimum inhibitory concentration (MIC) of the extracts against the listed organisms ranges from 1×104 µg/ᴄm3 to 4×104 µg/ᴄm3 and 3×104 µg/ᴄm3 to 5×104 µg/ᴄm3 for Crude extracts of the methanol and petroleum spirit respectively. Phytochemical examination of the extracts revealed the presence of alkaloids, steroids, saponins, glycosides, anthraquinones, tannins and flavonoids. These findings reveal broad spectrum activity of the plant stem-bark extracts.