The cardiovascular changes in the 10 minutes following antagonism of an atracurium-induced block were studied in 32 patients. A 5: 1 ratio combination of either 15, 35, 55 or 75 μg/kg neostigmine, with a corresponding dose of 3, 7, 11, or 15 μg/kg of glycopyrronium was used for antagonism. The least change in heart rate was with neostigmine 15 μg/kg with an increase of more than 15 beats/minute found in only one patient. Antagonism with 35, 55 and 75 μg/kg neostigmine mixture produced the greatest increase in heart rate at one minute and this was significantly different from the effect of the 15 μg/kg dose. Twenty out of 24 patients given the larger doses had heart rate increases in excess of 15 beats/minute and in nine patients this ranged from 30 to 52 beats/minute, representing increases of 46–80% above baseline values. Arterial pressure increases after antagonism were statistically significant in all four groups, with no between-group difference; these were clinically unimportant. When antagonising an atracurium-induced block with clinically useful doses of neostigmine, the standard 5: 1 ratio combination with glycopyrronium will result in an initial tachycardia.