Analytical methods for simultaneous determination of amprolium, carbadox, monensin and tylosin in surface water and soils were developed using LC-MS/MS coupled with solid-phase extraction (SPE). These four antibiotics are commonly used in animal feeding operations. Surface water sample was mixed with ~10% of methanol in volume, then passed through a Waters Oasis HLB cartridge. The cartridge was preconditioned with methanol and water. After loading the water sample, the cartridge was cleaned up using water, then eluted with methanol containing 2% formic acid. The eluate was analyzed using LC-MS/MS operated in electrospray positive ionization mode. The recoveries were 94% for amprolium, 95% for carbadox, 86% for monensin, and 94% for tylosin. For soil samples, methanol/2% ammonium acetate mixture was used to extract the four antibiotics from soil. The extract was cleaned up using the SPE procedure and analyzed by LC-MS/MS. The recoveries were 81 % for monensin, 91% for tylosin, 56 % for carbadox, and 44% for amprolium.