PIP: After a brief review of worldwide trends in the development and application of oral contraceptives (OCs), some of the results obtained in the laboratory of the Institute of Obstetrics and Gynecology in Leningrad, USSR, are presented. Experimental and clinical studies of modified synthetic steroids resulted in the development of Mezigepron, an original preparation that combines a strong contraceptive effect with a therapeutic action on certain gynecological disorders. Analysis of gestagenic and contraceptive properties of new progesterone derivatives revealed some highly active gestagenic agents, e.g., mepregenol diacetate. The Laboratory is studying the biological activity of 8-isoestradiol and other modified analogs of steroidal estrogens. These synthetic estrogens show a strong contraceptive effect with no significant uterotropic action. Such properties are important to the development of OCs which are free of any side effects. A new research program is studying the pharmacological properties of some synthetic analogs of luliberin. It is shown that short amino acid sequences produce a paradoxical antifertile effect which can be used for the development of new contraceptives. The biological activity of approximately 20 plant preparations was also studied. The greatest contraceptive activity was found in a combination of triterpenic glycosides.