A standardized near-drowning procedure was carried out on 16 adult normal sheep. Six milliliter sea water/kg body wt were introduced into the trachea by a tube. Ten minutes after near-drowning, eleven sheep were treated with HFV(HFVgroup), and the other 5 without HFV(NHFV group). Before near-drowning and at 5,15,30,40, 70,and 130 minutes afterward the measurement were made and it was found that: 1. Serum lipoperoxide(LPO) decreased for a short time, and then increased ten folds in both groups. 2. TXB_2 and 6-keto-PGF_(1?) increased in both groups. 3. pH decreased in NHFV groups(7.133—7.219). 4. PaO_2 decreased much mose in NHFV group. 5.PaCO_2 increased slightly at 5, 15 minutes after near-drowning; 6.K~+, Na~+, CI-increased slightly in both groups, and then returned to normal at 70 minutes after near-drowning. In HFV group; the changs of pulmonary ultrastructure after near-drowning were similar in both groups. The authors concluded that HFV showed some effects but is not satisfactory. We must find other treating methods to improve survival rate.