Standard ISO 7730, which is also known as European standard EN-ISO 7730, provides two alternative methods for the evaluation of the predicted mean vote (PMV): a calculation programme and a set of tables. In order to use the tables, the operative temperature must be calculated beforehand. The impression is given reading the standard that for a relative humidity of 50%, the two methods are equivalent, i.e. provide the same value for PMV, from the same initial values. In this paper, examples are given showing that the two methods are not equivalent. Differences between them are analyzed and a proposal made to introduce an amendment in the next revision of the standard.