Pupae of the darkling beetle, Tenebrio molitor, were irradiated in the standing wave of a CW-microwave field such that some of the pupae were positioned in the maximum plane of the E field while others were positioned in the maximum plane of the adjacent H field. The standing wave was produced by reflecting a plane wave at normal incidence from a metal plate that was suspended in the far field of a horn-irradiated anechoic chamber. Averaged energy dose rates for exposed pupae were determined through cooling-curve techniques by a thermistor in a 24-gauge hypodermic needle. Experiments were conducted at 4.0 and 5.95 GHz with calculated doses of energy of 37.8 to 1526 J/g in exposures of 5 min to 6-hours duration. Teratogenesis was found both for E-field and for H-field exposures and both for parallel and for perpendicular polarizations.