The effects of microwave radiation in reducing decalcification time were evaluated by measuring rates of calcium removal from samples of rat and cat teeth in 0.1 mol l-1 EDTA. In some cases, 3% glutaraldehyde was added to the decalcifying solution. Test specimens were placed in a microwave oven at 39 +/- 2 degrees C for repeated periods of 1-2 h. Control specimens were placed in a conventional oven at 39 degrees C for the same times or held at room temperature. The calcium removed during each treatment was measured using an atomic absorption spectrophotometer. There was no consistent difference between the results obtained with microwave radiation as compared with heating in a conventional oven, although in both cases decalcification was slightly faster than at room temperature. These results are attributed to thermal effects. No evidence for non-thermal effects of micro-radiation was found.