The capacity of the vaginal epithelium to absorb hormonal steroids and the ability of silicone elastomers to release these hormones at an almost constant rate form the basis for the use of synthetic rubber vaginal rings for therapeutic purposes. The first prototypes were made for contraception purposes but were later used for hormone replacement therapy (HRT) and, more recently, for the release of antiviral drugs. We have limited this article to contraceptive vaginal rings (CVRs), as their use in HRT was recently extensively reviewed and there are no publications on microbicide-delivering vaginal rings, available to date. Numerous models of CVRs have been studied, but only two have reached the market: NuvaRing® that releases ethinylestradiol and etonogestrel; and Progering® that releases progesterone, for use in lactating women. The main advantages of CVRs are: their effectiveness (similar or slightly better than the pill); ease of use, negating the need to remember a daily routine; the user's ability to control initiation and discontinuation; the nearly constant release rate allowing for lower doses; and, the good cycle control with the combined ring. It was expected that the CVRs would also allow avoidance of the first-pass effect on liver metabolism, but that hypothesis has not yet been confirmed. The main disadvantages are related to the mode of delivery: vaginal insertion may be unpleasant for some women; ring expulsion is not uncommon; the ring may be felt during coitus and be unpleasant for some partners; and, it may cause vaginal discharge and complaints. Although one ring model was associated with disruption of the vaginal mucosa, other studies with different models have not shown conclusive evidence that the ring causes vaginal lesions. 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