The simultaneous determination of 110 compounds including pesticides, hypnotics, local anesthetics, psychotropics, narcotics, etc., was examined by means of retention index on gas chromatography (GC). Temperature programmed GC using fused- silica capillary column CBP-1 (0.53 mm i. d.×12 m) was very effective in this study as compared with CBP-10 (0.33 mm i. d.×25 m) and some packed columns. All of the compounds except benzoximate, cloxazolam and oxazepam could be detected as good symmetrical peaks less than 100 minutes under the conditions of 120-250°C/(6°C/min) as oven temperature, 270°C as injection temperature, 0.2 kg/cm² as carrier gas (N₂) pressure (velocity, 90.9 cm/s) on CBP-1. A search window of these retention indices could be estimated about 20, then the discriminating powers of a combination of this data and TLC screening system mentioned earlier (Ref. 1), were 0.995, 1.00, 1.00, 0.996 and 1.00 in I, II, II', III and IV division, respectively.