The determination of five drugs, fenfluramine (FEN), N-nitrosofenfluramine (NFE), sibutramine (SIB), mazindol (MAZ) and phenolphthalein (PHP), was studied in slimming health foods using GC-MS/MS. These drugs have been detected at high rates, especially in slimming health foods. Prolonged or excessive consumption of non-approved or unauthorized pharmaceuticals may cause serious adverse health consequences. In this study, samples were extracted with methanol and ultrasonication. Analyses were performed by GC-MS/MS, using established MS/ MS parameters in the electron ionization (EI) mode and chemical ionization (CI) mode. In the EI mode, the recoveries of five drugs from several types of slimming health foods such as tablets, capsules and tea-bags spiked at 1 ῌg/mg (except PHP, spiked at 4 ῌg/mg) were in the range of 85.0῍110.7 and 100 ῌg/mg (except PHP, spiked at 200 ῌg/mg) were 94.9῍102.9, respectively. In the CI mode, good recoveries of 80.3῍102.2 (spiked at low concentration) and 92.8῍103.2 (spiked at high concentration) were also obtained. We evaluated the present method using four slimming health foods, in which drugs had previously been detected. The results were similar to the previous results. These findings indicate that the present procedure for evaluating five drugs in slimming health foods by means of GC-MS/MS is useful.