Effects of mild microwave treatment (1 hr, 37 degrees C) on the in vitro development of rat mechanically dissociated dorsal root ganglion (DRG) neurons were investigated to establish whether microwave irradiation effects exist on nervous tissue other than heat induced tissue fixation. Phase contrast microscopy and immunocytochemical neurofilament stainings did not reveal significant differences between irradiated (2 hr after isolation) and control cultures, maintained up till 21 days. The electrophysiological properties of microwave exposed and non-exposed DRG neurons were compared using the whole-cell patch-clamp technique. Control neurons, in culture for 0-12 days, were excitable. In cultured cells (1-12 days), microwaved 2 hr after isolation, the action potentials were similar to or slightly different from those of the control cells. No acute microwave effects were found on neurons irradiated after 1 day of culture. These results suggest that mild microwave irradiation has neither significant acute nor strong long-term effects on DRG culture development and DRG neuron membrane properties, consistent with the notion that microwave effects essentially are temperature effects.