Hepatic enzyme induction has been reported to increase lignocaine binding, alpha 1‐acid glycoprotein concentration and high density lipoprotein (HDL) cholesterol. In eight volunteers treated with rifampicin for 3 weeks there was no significant alteration in these three variables although their antipyrine clearance was significantly increased. In 10 patients with pulmonary tuberculosis treated with rifampicin (mean 5 months) the degree of serum protein binding of lignocaine, alpha 1‐acid glycoprotein and HDL‐cholesterol concentration was not different from that of matched control patients. These results suggest that differential induction of these variables may occur.