Blood samples of 20 schizophrenic patients, 20 of their first degree relatives and 43 normal subjects, both male and female, were taken and serum CPK estimation was done by using colorimetric sigma procedure. The schizophrenics and their 1st degree relatives had shown a significantly higher mean +/- S.D. CPK levels of 31.25 +/- 21.6 and 16.15 +/- 4.7 Sigma Units respectively as compared to 11.16 +/- 3.38 Sigma Units in normals (Cal. t = 5.73, tab. t = 1.65 at df = 61 and P less than 05). A significant difference between the CPK levels of male and female of the three groups was found (P less than .05). The males of normal, Schizophrenics and 1st degree relatives had significantly higher mean +/- S.D. CPK levels of 12.65 +/- 3.05, 47.4 +/- 18.73 and 19.5 +/- 1.93 Sigma Units respectively as compared to levels of 9.45 +/- 2.94, 15.10 +/- 4.33 and 12.71 +/- 2.47 sigma units in females of the corresponding three groups (P less than .05). Males of the patients and 1st degree relatives had shown higher levels than the females. A highly significant and positive correlation was found between the mean serum CPK levels of Schizophrenic patients and their 1st degree relatives (Correlation coefficient (gamma yx) = 0.79).