Highlights of papers presented at an international symposium on advantages and risks of oral contraceptives, and the details of the results of 2 studies are discussed. 1 study compared the effects of a combination of 30 mcg of ethinyl estradiol and 150 mcg of levonorgestrel with a reduced dose 3-phase combination of these hormones; it involved 489 women with 2777 menstrual cycles for a 6-month period. No pregnancies occurred. Missed menstruation occurred in 0.9% of the cycles with the 3-phase combination, contrasted with 2.3% of the 30/150 mcg combination group. Bleeding disorders were more frequent in the 30/150 pill group (15.7% vs. 10.1%). Spotting occurred in 8% of cases in both groups. The 3-phase pills proved to be safe and were preferred because they caused less bleeding. Another study compared the effects of 2 Swedish-made contraceptives by administering Neovletta (N) to 50%, Trionetta (T) to 25%, and Trionetta 28 (T 28) to another 25% of the 862 women with 6472 menstrual cycles who participated at 12 family planning centers in Sweden. T and N contain the same amount of estrogens, but T contains 40% less gestagen than N. The T 28 treatment also included 7 placebo tablets. Results showed that only 1 pregnancy occurred in the T group, despite a high rate of failure to take the pills (8.1-9.4%). Menstruation was normalized in both the N group (90.4%) and the T group (94.2%) reaching the normal 28 (+ or - 2) days cycle. Missed menstruation occurred in 0.6% of the T group as opposed to 2.3% of the N group. There was a significant difference in spotting and irregular bleeding between the 2 groups: 6.3%-15.8% for N and 3.0-9.0% for T. Also, there was a higher rate of bleeding problems for T 28 than for T. 8.6-8.8% of women in both groups quit the experiment because of complications, e.g., bleeding, nausea, headache, and hypertension. Both pills proved to be reliable and safe, but the new 3-phase preparation, T, is recommended because it does not reduce the beneficial HDL cholesterol as does N.