Background: Combined oral contraceptives (COCs) are hormonal contraceptives containing estrogen and progestogen in varying compositions. They have a wide range of side-effects including changes in serum lipid profiles and atherogenicity. The resultant effects of COCs on triglycerides, cholesterol, low-density lipoprotein-cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) vary for different studies. The atherogenic risks of COC users can be determined by calculating the lipid ratios which is more objective than using individual lipid parameters. Women with abnormal lipid profiles have increased risk of arteriosclerosis, coronary heart disease and even stroke. There was no local study using lipid ratios as a simple tool to determine the cardiovascular risks of women on COCs hence, the need for this study. Objectives: To determine the serum lipid profiles and cardiovascular risks of women on COCs in Ilorin, Nigeria. Design: This was a prospective cohort study with COC users as subjects while age and BMImatched non-users served as controls. Setting: Family planning clinics of a tertiary hospital, a secondary and two primary health centres in Ilorin, North Central region of Nigeria. Participants: Women who opted for COCs were recruited into the user group while the nonuser group consisted of healthy family planning clinic attendees who had chosen non-hormonal contraceptives Methodology: A total of 225 women who satisfied the inclusion criteria were recruited for the study by purposive non-probability sampling. One hundred and eleven (111) women who opted for COCs were recruited into the user group while 114 women who were healthy family planning clinic attendees on non-hormonal contraceptives and were age and BMI-matched with the users served as controls. The serum lipid profiles of both groups were determined at start ii (baseline), three and six months of follow up. A ratio of LDL and HDL was determined. The results were analysed using SPSS version 21.0 with appropriate tables and figures generated.