To the Editor.— The article by Halverson and associates (240:1870, 1978) regarding the toxicity of penicillamine omits one important factor of toxicity, that is, the dose the patient was receiving. This is one of the reasons that newer protocols for the administration of penicillamine stress the lower and slower dose schedules. It may well be that if the toxicity is dose related, and most rheumatologists are not using the highest doses that this group did, then the side effects stressed in this article are not pertinent to the present-day practice of using penicillamine for rheumatoid arthritis.