Thin-layer chromatographic separation and detection of 12 kinds of N-methylcarbamate insecticides, which are classified as poisonous chemicals and are widely used in Japan, were examined using the layers of silica gel, alumina, and polyamide. Two chromatographic systems : (1) aceton-hexane (1 : 4) on alumina layer and (2) water-methanol (5 : 5) on polyamide layer, with detection by p-nitrobenzenediazonium fluoroborate-KOH or bromine-fluorescein method, were found to be the most suitable for the analysis of these compounds.