We studied the effects of succinylcholine (SCC) on serum levels of myoglobin (Mb) and CK in children under halothane or enflurane anesthesia. Forty-five children, aged 2 years 11 months to 12 years 6 months were subjected to this study. They were divided into four groups; the two groups were injected with SCC 1 mg.kg-1 intravenously to facilitate tracheal intubation and maintained with halothane (Group SH) or with enflurane (Group SE). The other two groups were intubated without the aid of SCC and maintained with halothane (Group H), or with enflurane (Group E). Mb was analyzed by an antibody radioimmunoassay technique and CK was analyzed by a modified Rosalki's method. While Mb increased in all four groups, the increase was pronounced in the SCC groups (60 min value of Group SH 2192 +/- 639 ng.ml-1, Group SE 1722 +/- 436 ng.ml-1, mean +/- SE), and the increase was significantly smaller in SCC free groups (Group H 40 +/- 12 ng.ml-1, Group E 43 +/- 9 ng.ml-1). The CK value increased only in the SCC groups to 174.1 +/- 32.8 IU.l-1 in Group SH, and to 193.6 +/- 35.7 IU.l-1 in Group SE at 60 min, respectively. These results indicate that increases in Mb and CK values were mainly induced by SCC injection and that SCC might play some roles in development of malignant hyperthermia.