Male mice (25-30 g) were injected (ip) with either 0, 3.5 X 10(-6), 17.5 X 10(-6), or 26.25 X 10(-6) mol/kg of either tricyclohexyltin bromide (TCT) or triphenyltin acetate (TPhT) in a corn-oil vehicle. The mice were tested for maximal electroshock seizure (MES) at 0.5, 4, 24, and 96 h following exposure to the organotin compounds, and the durations of seizure phases were measured and used to assess seizure severity. No significant changes in seizure-grade distribution, as compared to controls, were observed in any of the TCT- or TPhT-treated groups at any of the time points examined. No significant changes in the duration of seizure phases, as compared to controls, were observed in animals dose with 3.5 X 10(-6) mol/kg of TCT or TPhT at any of the time points evaluated. At 0.5 h following exposure, the mice dosed with the two higher levels of TCT or TPhT exhibited increases in MES severity. At 4 and 24 h following exposures, the mice exposed to the two higher dose levels of TPhT exhibited decreases in MES severity, followed by a recovery of normal seizure severity at 96 h. Conversely, the animals dosed with the higher dose levels of TCT exhibited at increased MES severity at 4, 24, and 96 h following exposure. These results, in combination with those in the preceeding paper (Doctor and Fox, 1982), reveal that at equimolar doses TCT And TPhT possess a different spectrum of action than the tri-n-alkyltins.