The concentration of P-immunoglobulins (P-IgG, P-IgA, P-IgM), P-orosomucoid, S-creatine kinase (S-CK), and S-follicle stimulating hormone (S-FSH) was investigated in seven subjects exposed to 100 p.p.m. white spirit, 6 hrs daily during 5 days while 5 subjects were used as unexposed controls. The mean values for S-CK concentration in the exposed group increased significantly with 59% and 76% above the base-line (O-hr value) 96 hrs and 168 hrs, respectively, after the start of the exposure (P less than 0.05), while the mean values for S-FSH concentration decreased significantly to 11% and 9% below the base-line after 24 hrs and 96 hrs (P less than 0.05), respectively. S-CK concentration and S-FSH concentration in the control group remained unchanged. A marked interindividual and intraindividual variance in S-CK concentration and S-FSH concentration was observed. No changes in the concentration of immunoglobulins and orosomucoid were observed in both groups during the experiment. The mechanisms for the changes are at present only speculative, but solvent induced changes in muscle cell membranes with subsequent enzyme leakage seem the most reasonable explanation for the increase in S-CK concentration, while an effect on the hypothalamic FSH releasing hormone may explain the decrease in S-FSH concentration.