The trypsin inhibitor activities (TIA) of various potato cultivars were evaluated by measuring the inhibition of trypsin inhibitor activity using N-benzoyl-DL-arginine-p-nitroanilide (BAPNA) as substrate. The TIA values of 5 potato cultivars (1.99 to 2.88 mg/g) were significantly different among cultivars (p<0.05). When the TIA values of commercially processed potatoes were determined, no TIA was detected. During cooking, the $IT_{50}$ (time required to reach 50% inhibition of TIA) values were decreased as heating temperature and time increased. The ITso of moist heating was estimated to be 0.34 min at $100^{circ}C$, whereas for deep-fat frying the $IT_{50}$ was 0.13 min at $180^{circ}C$ and 5.28 min for oven baking at $100^{circ}C$. The $IT_{50}$ value of microwave cooking was 0.194 min at medium heat, and which was similar to that of pressure cooking at $120^{circ}C$ (0.185 min). Moreover, there was a negative relationship between temperature (${geq}80^{circ}C$) and $IT_{50}$ values ($R^2=0.99$, p<0.01). The TIA of potato was completely inactivated by moist heating at $100^{circ}C$ within 5 min, whereas the pressure cooking at $120^{circ}C$ and deep-fat frying at $180^{circ}C$ within 60 and 30 sec, respectively. Based on our results, deep-fat frying is the most effective cooking method to reduce TIA in potatoes.