The adrenergic and dopaminergic systems and 5-hydroxytryptamine levels were studied in four groups of pregnant : group I of 25 first trimester normotensives, group II of 15 second trimester normotensives, group III of 15 third trimester normotensives, Group IV of 15 with pregnancy-induced hypertension. Blood samples were taken from the fasting ambulatory women. Plasma norepinephrine (NE) levels were 196±66pg/ml, 202±49pg/ml, 188±49pg/ml, 214±75pg/ml, respectively. There was no significance among each group. Plasma 3,4-dihydroxyphenylacetic acid (DOPAC) levels were significantly higher in pregnancy-induced hypertension than in the other groups. (648±196pg/ml vs. 483±102,497±92 and 501±139pg/ml). Plasma 5-hydroxytryptamine (5-HT) levels were significantly higher in case of pregnancy-induced hypertension than in the other groups. (122±22ng/ml vs. 93±26,99±18 and 94±22ng/ml). These data may suggest that the serotonergic and/or dopaminergic systems may play important roles in pregnancy-induced hypertension.