Abstract: The disclosed invention provides methods and compositions ulilizing L-.alpha.-amino acids for enhancing the rate of penetration through the skin of both topical medicaments and of drugs employed for systemic administration. Fifteen L-.alpha.-amino acids were tested and found to enhance the rate of penetration of levonorgestrel through hairless mouse skin. These were Tryptophan, Glutamic Acid, Glycine, Proline, Alanine, Serine, Arginine, Aspartic Acid, Leucine, Isoleucine, Cysteine, Valine, .alpha.-Aminobutyric Acid, Norvaline and Norleucine. The effect of pH on the rate of penetration of the various amino acids was also examined and found to be unpredictable overall.