OBJECTIVE To study the changes in serum lipids, serum chemistry, blood pressure, and body weight in long-term users of subcutaneous contraceptive implants releasing the progestin ST 1435. METHODS The study was done in the outpatient clinic of the City Maternity Hospital, Helsinki, Finland. Subdermal implants releasing the progestin ST 1435 were inserted in 30 women for 2 years of use. Healthy women aged 19-35 used the implants for contraception. Measurements of body weight and blood pressure were made and blood samples for lipid analysis (total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides) and serum chemistry were taken before insertion of the implants and every 6 months thereafter until removal. Results are reported for 30 subjects after 6 months of use, 25 subjects after 12 months, 13 after 18 months, and 12 after 24 months. RESULTS Blood pressure and serum chemistry, ie, liver enzymes and electrolytes, remained unchanged. Slight weight gain occurred, but was not statistically significant. No statistically significant changes were found in lipids or lipid ratios when comparing the values during use of the implant with the pre-treatment values. CONCLUSIONS The progestin ST 1435, used parenterally for contraception or progestin therapy, had no adverse effects on serum lipids, blood pressure, or body weight, which are known to be risk factors for coronary artery disease. The steroid had no effects on serum chemistry determinations in long-term use.