This study was conducted to evaluate te working times of seven elastomeric impresion materials according to their detail reproduction and dimensional accuracy. Impressions were made of a standard ADA Specification No. 19 die at 30 second intervals until they were no longer workable. The detail reproduction and dimensional stability of these impressions were evaluated according to the ADA Specification No. 19 criteria and the dimensional stability was analyzed. It was found that the working times of the impression materials according to detail reproduction generally agreed with those estimated according to dimensional stability but not with the manufacturers' suggested working times.