A review of the history of contraception with intrauterine devices characteristics of present devices and directions of current research is presented. The serious need for population control is not yet being met by todays inconvenient ineffective or unsafe methods. Intrauterine devices have been best for international family planning programs because they are cheap easily installed and provide continuous protection. There are many different models that have been and are being used with different effectiveness and complication rates. The most commonly used today is the Lippes Loop with a pregnancy rate of 2.8/100 years of woman use and an expulsion rate of 10.4. Most of these failures occur in the first few months of use after which these rates are greatly reduced. The removal rate because of bleeding or pain for the Lippes device is 14.0. Other devices commonly used have pregnancy rates ranging 1.3-4.7 expulsion rates of 2.6-25.8 and removal rates of 13.5-22.1. Expulsion is directly related to the size and design of the IUD and the age and parity of te recipient. It is important to match the size of the device used to the individual characteristics of the patient. Research is seeking a design that will implant itself in the endometrium to resist expulsion but not too deeply so that it is covered. Removal for bleeding and pain remains the most frequent complication of the IUD and it partly depends on the skill of the inserting physician and how well the patient is psychologically prepared for side effects in the first months of use. Pregnancy is the most significant IUD complication. The key to an effective IUD is an understanding of its antifertility mechanism which has thus far eluded researchers. The IUD prevents implantation of the blastocyst in the uterine wall which may be due to a foreign-body reaction in the endometrium. IUDs with copper cause a greater reaction than plastic devices and provide hope for a very effective device; particularly the T-shaped design which resists expulsion. The most promising new IUD is the Dalkon Shield. It has small projections that imbed in the endometrium and a broad surface for contact with the uterine wall. In preliminary experiments the pregnancy rate with this device was 1.1 the expulsion rate 2.3 and the removal rate 2.0 much lower than that with any other device yet developed. It is concluded that IUDs such as the Dalkon Shield can provide safe contraception with high effectiveness.