1. Almitrine at a dose of 0·5 mg h−1 kg−1 given intravenously over 2 h had no effect on resting ventilation in normal males.
2. There was a small, but insignificant, rise in the hypercapnic drive to breathe as compared with placebo.
3. A large rise in the hypoxic drive to breathe was seen in response to almitrine.
4. These findings support the claim that almitrine has its action on ventilation via the peripheral chemoreceptors.
5. No correlation between blood levels of almitrine and the rise in hypoxic response was seen.