Injectable progestogen, norethisterone enanthate (NET-EN, 200 mg/ml at 60-day intervals), was administered to one-hundred-fifty women for two years as a method of contraception. Blood levels of acid phosphatase (ACP), alkaline phosphatase (AP), glutamate pyruvate transaminase (GPT), glutamate oxaloacetate transaminase (COT), acetylcholinesterase (AChE) and sialic acid were determined in all the subjects to ascertain whether NET-EN therapy causes any adverse metabolic effect or damage to the functional status of the liver. NET-EN contraception did not alter the liver function enzymes, but there is a significant increase (P < 0.001) in AChE activity after two years. Serum sialic acid level showed a transient increase up to one year, which however returned to control level later. The mechanism responsible for these changes and whether the rise in sialic acid and AChE activity are related to any pathological condition remain unclear at this stage. © 1984 Geron-X, Inc.