A convenience sample of California registered dietitians (RDs) (n=253) completed a survey investigating the perceived knowledge, attitudes, and practices of RDs who had or had not received formal training in use of dietary supplements. We also examined whether differences existed between RDs registered before or after 1997, when the American Dietetic Association began requiring that dietetics curricula include basic knowledge of dietary supplements. Statistical analysis included analysis of variance and χ 2 analysis. Among this sample of RDs from California, those registered before 1997 (n=194) were more likely (P<0.05) to agree that they are knowledgeable regarding supplement use, safety, interactions, and contraindications than those registered after 1997 (n=46), and were more likely (P<0.05) to assess client use. Among this sample of RDs from California, those reporting that they had received formal training in dietary supplements (n=145) were more likely (P<0.05) than those who had no formal training in supplement use (n=105) to agree that they are comfortable discussing supplements with the public; are knowledgeable regarding uses, safety, interactions, and contraindications of supplements; and assess client use. Providing RDs professional education opportunities on supplements continues to be warranted.