Plasma prostaglandin (PG) and thromboxane (Tx) levels from bronchial asthmatic patients were assayed by 9-anthryldiazomethane reversed-phase high-performance liquid chromatography method. TxB2 levels from stable bronchial asthmatic patients were significantly higher than those from normal healthy subjects. PGF2 alpha levels were significantly elevated in atopic patients compared with nonatopic ones. PG patterns differed between asthmatic and nonasthmatic conditions in the same patients. PGF2 alpha levels were significantly elevated in the patients with spontaneous attacks compared with those without attacks and 6-keto PGF1 alpha levels were significantly lower in bronchial asthmatic patients having attacks than in the patients without attacks. There were no significant differences of PG levels between mild and moderate asthmatic subjects. Aminophylline injection in patients with mild spontaneous attacks had no significant effects on PG levels which were compared before and after injection.