A transdermal hormone delivery system (THDS) is disclosed. The THDS is useful for control of fertility and as therapy for a variety of diseases and conditions treatable by robust delivery of progestin and estrogen hormones, particularly the progestin, levonorgestrel. The THDS comprises a backing layer, an adjoining adhesive polymer matrix comprising an effective amount of at least a progestin hormone, delivery of which is enhanced by one or more skin permeation enhancing agents present in pre-determined amounts. The THDS is capable of providing effective daily doses of progestin and estrogen hormones from a small surface area in contact with the skin, e.g., less than 20 square centimeters. Methods of fertility control and various types of hormone replacement therapy utilizing the THDS are also disclosed.