The insecticidal constituents of hexane-soluble fraction from a methanolic extract of the seeds from Myristica fragrans (Myristicaceae) against adult females of Blattella germanica (L.) (Dictyoptera: Blattellidae) were analyzed by gas chromatography and gas chromatography-mass spectrometry. The insecticidal activity of 13 Myristica seed compounds against female B. germanica was examined by using the filter-paper contact toxicity and vapor phase toxicity bioassays. Results were compared with those of the other 23 known compounds of Myristica seed and currently used insecticides: dichlorvos, deltamethrin, permethrin, and propoxur. In contact toxicity tests using female B. germanica, (1S)-(−)-β-pinene (0.06 mg/cm²) was the most toxic insecticide, based on 24-h LD₅₀ values. The insecticidal activity of this compound was comparable with that of permethrin (0.05 mg/cm²). (1R)-( )-Camphor, (1S)-(−)-camphor, dipentene, (1R)-( )-β-pinene, and ( )-α-terpineol (0.10–0.14 mg/cm²) were more toxic than propoxur (0.19 mg/cm²). (E)-Sabinene hydrate and propoxur were almost equitoxic. Potent insecticidal activity also was observed with (R)-( )-citronellal, (S)-(−)-citronellal, (R)-(−)-α-phellandrene, (1S)-(−)-α-pinene, (1R)-( )-α-pinene, and safrole (0.27–0.48 mg/cm²). In vapor phase toxicity tests, the compounds tested were effective in closed but not in open containers. These results indicate that the effect of these compounds was largely a result of action in the vapor phase. Myristica seed compounds described merit further study as potential insecticides or as leads for the control of cockroaches.