Analyses of 2002 National Health Interview supplement on complementary and alternative medicine (NHI%AM) indicate that approximately 38 million adults in the US (18.9% of the population) used natural herbs or supplements in the preceding 12 months, but only one-third told their physician about this use. The objectives of this study are: (i) to determine subpopulation rates of patient-physician communication about herbal product and natural supplement use and (ii) to identify the relative influence of patient factors and interaction factors associated with patient-physician communication about herb and supplement use. Logistic secondary analysis was done by using the complementary and alternative medicine supplement of the 2002 National Health Interview Survey. Subjects were a random stratified sample of US adults who used herbs in the past 12 months (n = 5 196) and self-reported rates of disclosure to physicians about herb and supplement use. Results show that disclosure rates were significantly lower for males, younger adults, racial and ethnic minorities and less intensive users of medical care. Across subpopulations, disclosure was the exception rather than the norm. Given the potential risks of delayed or inappropriate treatment and adverse drug reactions and interactions, physicians should be aware of herb and supplement use and counsel patients on the potential risks and benefits of these treatments.