In two previous studies, the times required to approve new drugs in Canada, Australia, Sweden, the United Kingdom and the United States during the periods 1992 to 1995 and 1996 to 1998 were compared. However, during each of these two periods, only a fraction of the drugs that were approved in any of the countries were approved in all of them. Because an analysis based solely on drugs approved in all the countries would provide additional information, data from the previous studies have been used to compare drugs approved in each of Canada, Australia, Sweden and the United States during the period 1992 to 1998. In addition, applications that received a 'priority' or a 'standard' review by the United States Food and Drug Administration were analyzed separately to determine whether differences between the countries diminished for drugs considered to be of potentially greater therapeutic value. For the 87 drugs identified as being approved for marketing in all four countries during the period 1992 to 1998, approval times in Canada and Australia were not significantly different, but both Canada and Australia had significantly longer times than those of the United States and Sweden (P<0.001). Of the 87 drugs, 37 (43%) received a priority review in the United States. In both the priority and standard review categories, the Australian and Canadian median approval times were significantly longer than those in Sweden and the United States. The results demonstrate that, in general, both priority and standard new drug applications are reviewed more expeditiously in Sweden and the United States than in Canada. Canadian patients continue to experience delayed access to potentially valuable medicines.