Effect of heating two kinds of rapeseed and their meal under various conditions was examined on destruction of thioglucosides contained in them which may impart toxity and unpalatability to them by changing themselves into oxazolidinethiones. The thioglucosides were easily destroyed by autoclaving, of which the optimum conditions were; 150min. at 120°C for Brassica napus seed, 50 min. at 120°C for B. napus defatted meal, and 100min. at 100°C for B. campestris seed oil meal; whereas dry-heating treatments were not only ineffective but also resulted in more serious toxity and unpalatability than the untreated sample.