The cardiovascular effects of two organophosphorus, paraoxon and soman, as well as of antidotes advocated in the treatment of these intoxications have been investigated using a computerized analysis of arterial blood pressure in conscious unrestrained rats. Intravenous administration of paraoxon as well as of soman produced a marked, sustained and dose-related increase in blood pressure associated with a bradycardia. Pyridostigmine, a quaternary carbamate, neither altered blood pressure nor heart rate. Benzodiaxepines, such as diazepam or loprazolam, and atropine induced a dose-dependent tachycardia while pralidoxime decreased heart rate. A complete therapeutic scheme including the intravenous administration of pyridostigmine 10 min. before a postpoisoning therapy made of pralidoxime, diazepam and atropine induced a transient tachycardia, which was followed, after a return to control values, by a second and more stable tachycardia concurrently to a slight hypertension. Postpoisoning therapy alone suppressed the pressor effect of soman within a few minutes after its administration. Afterwards, this therapy reduced the importance of the cardiovascular effects produced by soman. Pyridostigmine pretreatment decreased the protection afforded by postpoisoning therapy in soman-intoxicated rats. These results show that postpoisoning therapy with pralidoxime, diazepam and atropine has a noteworthy efficacy against cardiovascular manifestations of soman intoxications in the rat.