Abstract Selective cyclo-oxygenase (COX)-2 inhibitors were developed with the hope of producing lesser gastrointestinal (GI) side effects as compared with the conventional nonsteroidal anti-inflammatory drugs (NSAIDs). Soon after their introduction into the market, the sales of celecoxib and rofecoxib went up considerably. Most of this was attributed to the results of the Celecoxib Long-term Arthritis Safety Study (CLASS) and Vioxx Gastrointestinal Outcome Research (VIGOR) trials. However, several discrepancies were noted in the presentation of the actual trial results submitted to the US Food and Drug Administration (FDA) and those used for the purpose of publication in scientific journals. These issues were discussed subsequently by the way of scientific communications. Moreover, with increasing use of these agents, evidence of their adverse effects is coming to light. The present review aims at discussing the above issues, with emphasis on the results of the CLASS and VIGOR trials.