The Harris-Benedict equation, as cited in a selection of textbooks of medicine, surgery, and nutrition, was compared with the original monograph published by the Carnegie Foundation. A significant amount of variation was found in published versions of this equation. Of 24 published versions, eight were sufficiently variant to produce errors of 7% to 55% in calculations of nutrition requirements. The error is usually in the constant term for one of the two Harris-Benedict equations. Either the constant term for men is increased to a value approximately the same as for women, or the constant term for women is reduced to be approximately equal to that for men. The primary reason appears to be the lack of availability in medical libraries of the original Carnegie Foundation publication by Harris and Benedict. (Journal of Parenteral and Enteral Nutrition16:566-568, 1992)