Objective and design.To compare the total and age‐specific incidence of thyrotoxicosis, as well as the incidence of the individual types of thyrotoxicosis [i.e. thyrotoxicosis of Graves' type (GD), toxic nodular goitre (TNG) and solitary toxic adenoma (STA)] in Malmö during the years 1988–1990 to those of a previous study in 1970–1974.Setting.The town of Malmö in southern Sweden.Subjects.All patients from the Malmö population treated for thyrotoxicosis (GD, TNG and STA) for the first time during the 3‐year period 1988–1990 were included.Results.Overall, 299 (263 females and 36 males) new cases of thyrotoxicosis were diagnosed in 1988–1990, corresponding to a mean annual incidence of thyrotoxicosis of 43.0 per 100000 inhabitants. The incidence of GD was 22.3, of TNG 16.0 and of STA 4.8 per 100000 per year. Comparing age‐ and sex‐standardized incidences to the results in 1970–1974, there was a significant increase (P<0.001) in the mean annual incidence of thyrotoxicosis in the total material as well as in TNG. In addition, there was an increase in GD in females younger than 50 years (P<0.01), whereas in TNG/STA, an increase was seen in females of 50 years or older (P<0.001). The incidence figures in males were not significantly changed. There was a higher proportion of smokers in females with GD compared to females with TNG (P<0.001) and STA (P<0.05).Conclusions.The total incidence of thyrotoxicosis, as well as the incidence of GD in females younger than 50 years and the incidence of TNG/STA in females of 50 years or older, has increased in Malmö during the period from 1970 to 1990. The increase was probably caused by several factors such as more sensitive diagnostic tools and GD changes in smoking habits, but additional unknown factors might