Morphogenetic activity (budding region regeneration, foot regeneration, tentacle regeneration, spikes, separation, and waist) was observed in Hydra oligactis with two tandemly arranged gastric regions (2g hydras) following exposure to a commercial ethylene dibromide (EDB) mixture. First-stage budding hydras were selected for this study. Animals were deprived of food 24 h prior to grafting and observed at 24, 48, and 72 h after grafting. The artificial pond water (APW) group was not treated with any chemicals prior to grafting. The acetone/APW group was pre-exposed to a concentration of 20 mg/L of acetone/APW 24, 48, and 72 h prior to grafting and observed at 24 h intervals for a three-day period. The EDB: acetone/APW group was exposed to a mixture containing 5 mg/L of EDB and 15 mg/L acetone for 24, 48, and 72 h prior to grafting and observed at 24-hr intervals for three days. All animals were incubated at 19 +/- 2 degrees C. Ethylene dibromide caused a significant decrease in 2 degrees foot regeneration at the 72 h observation interval for animals pre-exposed to EDB for 48 and 72 h. There was also a significant correlation between pre-exposure and a decrease in the number of 2 degrees feet regenerated. Tentacle regeneration was significantly suppressed following a 24-h pre-exposure to EDB. Waists at the graft border significantly increased at the 48 and 72 h observation times and separation of the graft border appeared at 72 h after grafting following 72 h pre-exposure of the animals to the chemical.