This research was study antibacterial activity of methanol extract from bark of samrong (Sterculia foetida L.) against Escherichia coli ATCC 25922, Proteus mirabilis, drug resistant Pseudomonas aeruginosa and Serratia marcescens compare to ampicillin and tetracycline. The experiment was determined value of minimal inhibitory concentration (MIC) by agar diffusion susceptibility test at concentration of 0.0782-80 mg/ml. Methanol extract from bark of samrong (Sterculia Foetida L.) was against all of gram negative bacteria. Methanol extract from bark of samrong (Sterculia Foetida L.) was against gram negative bacteria at the MIC between 10-20 mg/ml by could inhibited E. coli ATCC 25922 and S. marcescens better than P. mirabilis และ P. aeruginosa MDR. Also, the efficacy of tetracycline against bacteria was significantly higher than ampicillin at significance level of 0.05.