The frequency with which agranulocytosis was associated with mianserin in New Zealand was calculated, by two methods, from spontaneous reports to the Intensive Medicines Monitoring Programme (IMMP)--one gave a frequency of 1 in 1354 (95% CI 1 in 3145 to 1 in 685) and the other gave a rate of 1 in 1743 (95% CI 1 in 2895 to 1 in 1116). There were 3 deaths. Age and dose seemed to be related to occurrence of agranulocytosis. The frequency of the complication seemed to be higher than that reported for other countries, perhaps because higher doses were prescribed in New Zealand but also perhaps because of a selection bias in surveys elsewhere. The occurrence of agranulocytosis with mianserin in New Zealand is higher than that of white-cell dyscrasias reported with use of chloramphenicol, phenylbutazone, and oxyphenbutazone, and although the case-fatality rate of agranulocytosis is lower with mianserin than with the other drugs, the overall mortality rate may be higher.