This paper is related to clarify the safety of jogging in the early morning. Cardio-vascular and serum biochemical analysis were carried out as follows in 10 healthy male students of Hiroshima Univ. dept. Physical Education. Design of experiment was, A: early morning at fast, B: early morning at carbohydrate (100 g) intake, C: two hours after lunch. Intensity of exercise was 60% VO₂max and duration was thirty minutes. Items of examination were a) postural test and cold pressor test in the early morning and afternoon, b) HR and BP during exercise, c) serum biochemical parameters at before and after (BS, IRI, FFA, CPK, UA, LA).
　Group A showed the lower heart rate, blood pressure and higher reactivity to postural and cold pressor test than other two groups. Group A resulted in lower HR and BP than those observed in group B, C during initial 15 minutes. In group A, lower serum BS and IRI response at both before and after, and higher levels of FFA at after exercise were observed.
　These results suggested that a remarkable delay of cardio-vascular adaptation and rise of FFA might be a risk factor against the safety of exercise in the early morning.

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