During the 5-year period 1975-1979, 41 out of a total of 157 patients treated for 'organophosphate poisoning' (26%) were admitted to intensive care units. Treatment comprised atropine (0,02-0, mg/kg every 15-30 minutes or 0,02 - 0,08 mg/kg/h by continuous intravenous infusion), intermittent mandatory ventilation (IMV) with continuous positive airways pressure (CPAP) where indicated, and general supportive measures including adjustment of electrolyte, fluid and acid-base balance. Oxime-type cholinesterase reactivators were administered to 10 patients. Serum cholinesterase (S-ChE) and erythrocyte acetylcholinesterase (E-AChE) activities were monitored continuously. Despite intensive therapy, 5 patients (12%) died. IMV and CPAP proved to be a near-ideal method of mechanical ventilation. Atropine administered by continuous infusion was found to be superior to intermittent administration during the acute phase, while oral administration of atropine proved adequate thereafter. Oxime-type reactivators were not found to be of any significant value. Clinical recovery (the point at which atropine could safely be discontinued) generally correlated with a recovery of E-AChE activity to 30% or more of normal. Sudden deterioration due to possible 'endogenous re-intoxication' was observed in some patients days after the initial exposure to an organophosphate insecticide.