Postoperative muscle pain and transient increase in serum potassium condcentration is well known to occur in man following intravenous administration of succinylcholine. Crawford (1971) and Datta et al, (1977) reported that the incidence of muscle pain and degree of fasciculation following administration of succinylcholine is lower in pregnant than in nonpregnant women. However Hegarty (1956) reported that there is no relationship between the incidence of muscle pain and the degree of fasciculation. To study the incidence of muscle pain and degree of fasciculation after intravenous injection of succinylcholine in pregnant and non-pregnant women, we studied two groups, an experimental pregenant group and a non-pregnant group as a control. The following results were obtained: The incidence of muscle pain was 73.3% in the non-pregnant group and 56.0% in the pregnant group, but no statistically significant difference was noticed between the two groups. 2) The most common sites of pain were, in. order of frequency, the neck, legs, entire body, back, arm and chest. There was no significant; difference between the two groups. 3) The most common sites of pain were, in order of frequency, the neck, legs, entire body, back, arm and chest. There was no significant difference between the two groups. 3) The muscle pain usually appeared within 24hours after the operation. The duration. of muscle pain was mostly less than 72hours. There was no significant difference between the two groups. 4) There was no significant relationship between the anesthetics and the incidence of postoperative muscle pain in both groups. 5) There was no significant relationship between the degree of muscle fasciculation and the incidence of muscle pain in both groups. 6) The serum potassium level following administration of succinylcholine was almost unchanged in both groups.