A maximum of six live mice, mouse cadavers, prolate spheroids molded from muscle‐equivalent tissue, or saline‐filled culture flasks, were exposed to continuous wave radiation in a TEM cell at frequencies between 200 and 400 MHz. Whole‐body average specific absorption rate (SAR) was determined from power meter measurements of incident, reflected, and transmitted powers. The SARs for both live mice and cadavers were approximately twice that for the prolate spheroid models, and when housed in Plexiglas restraining cages, about 2 1/2 times greater. An error multiplying factor is identified, that quantitatively expresses how SAR data obtained by the three ‐power‐meter method becomes progressively more noisy as the irradiation frequency is lowered or as the TEM cell cross section is increased. Copyright © 1983 Wiley‐Liss, Inc., A Wiley Company