Phasic oral contraceptives (OCs) provide a physiological approach to contraception and most closely approximate the ideals of a combined OC with the lowest possible doses to avoid the metabolic risks of estrogens and progestins, maximal contraceptive protection, and satisfactory cycle control. Earlier studies have demostrated the decline in myocaridal infarct and thromboembolic disease with reduction of ethinyl estradiol (EE) from 50 to 30 mcg, the correlation between progestin dose and cardiovascular and cerebrovascular deaths, and the effects of progestins derived from 19 nortestosterone in reducing the beneficial high density lipoprotein (HDL) cholesterol. The preparation SH B 264 AB for example provides a 1st phase daily dose of 30 mcg EE and 50 mcg levonorgestrel, a sufficient dosage because of the low probability of ovulation but 1 which attempts to mimic the follicular secretion needed for endometrial growth. Daily doses in the 2nd phase increase to 40 mcg EE and 75 levonorgestrel, each of which is capable alone of inhibiting ovulation. The progestin causes a supplementary hypothalamic inhibition and renders the cervical mucus too viscous for sperm penetration, while the EE augments the hypothalamic inhibitory effect of the progestin, prevents release of luteinizing hormone releasing hormone, and suppresses the luteinizing hormone peak by increasing the pituitary threshold to hypothalamic stimulation. The total dose of SH B 264 AB is at least 30% less than that of other OCs. The Pearl index is 0.0-0.6, not quite as good as that of normal dosed OCs. The duration of menstrual bleeding appears unchanged even after prolonged use, while the amount of bleeding is slightly decreased. Amenorrhea and intermenstrual bleeding are rare. The good cycle control occurs because the steroid levels administered in the triphasic pill mimic those of ovarian secretion, leading to better endometrial development. The effects of triphasic pills on glycemia and insulin levels are very weak and are not statistically significant, while their slight estrogen dominance means that they have very slight effects on the level of HDL cholesterol. They cause a slight increase in triglyceride levels, minimal variation in coagulation parameters, a weak variation in factors VII, VIII, X, and plasminogen, and a slight decrease of antithrombin III. Triphasic OCs induce minimal augmentation in activity of the renin-angiotensin system, and in most cases do not affect blood pressure. Because of their estrogenic dominance, triphasic pills improve acne but may be associated with breast problems, water retention, dysmenorrhea, and premenstrual syndrome with irritability, nervousness, and headache. Triphasic pills are indicated for women beginning OCs, women with poor cycle control under other OCs, women at high cardiovascular risk, women with acne, and women whose current OCs cause oily skin, hirsutism, reduced libido or other symptoms. Contraindications for the triphasic pill in addition to the usual factors include benign breast disease, premenstural syndrome, dysmenorrhea, or polycystic ovarian syndrome.