The purpose of this study was to investigate the changes of salty taste sensitivity (STS) during the physicaleducation (P.E.) swim class in outdoor, summer. Eight healthy young males (age: 16 years) were volunteered to thisinvestigation and swam (approximate 400 m for 70 minutes) in July (temperature: 31.2 ± 0.6 ℃ ). Participant's STS,urinary electrolyte, ration of dehydration and the degree of salty appetite (DSA) were measured before and after P.E.(respectively, Pre and Post). DSA at Post was significantly higher than that of Pre. STS, urinary Na / Cr and urinaryCl / Cr at Post were significantly lower than that of Pre. STS at Post significantly increased even if that ration of dehydration(0.45 ± 0.20 %) was not enough to the level of concern in summer.