Accompanied by the introduction of new regulations in environment and foodstuffs fields, various kinds of mixed standard solutions of organic substances are on the market in Japan for the convenience of analysts. However, since these standard solutions are not certified, it is necessary to evaluate their reliability. In the present study, in order to evaluate the validity of the concentrations of the standard solution on the market, 3 mixed solutions (10 μg/mL) were examined ; these contained 68 pesticides each. They were diluted with hexane to prepare 1 μg/mL each, and were measured by an internal-standard method using GC/MS. The measurement values of 68 the pesticides between the 3 mixed standards were analyzed by one-way layout analysis and by multiple comparisons. As a result, the values of 30 out of the 68 pesticides were significantly different from each other, which indicates that the analytical results obtained using these standards are deemed to be significantly different. From these results, it was confirmed that an improvement in the reliability of the concentrations in standard solutions and disclosure of the preparing process of standard solutions is strongly required.