1. Further observations from an earlier study in which phenobarbitone in a dose of 180 mg daily was administered to ten normal men and women for 3 weeks are reported. There was a significant increase in plasma high-denity-lipoprotein (HDL) cholesterol concentration and in the concentration of both total plasma and low-density-lipoprotein (LDL) apolipoprotein B.
2. There was no change in the ratios of the cholesterol: apolipoprotein B and triglyceride: apolipoprotein B in LDL.
3. There was no significant change in plasma very-low-density-lipoprotein (VLDL) apolipoprotein B concentration and the proportion of lipid and apolipoprotein B in VLDL remained unchanged.
4. There was no change in the ratio of HDL:LDL cholesterol concentrations.