Throughout the 20th century many different patterns of asthma mortality have been observed. Following relatively stable asthma mortality rates during the first half of this century, there has been a gradual increase in asthma mortality in many countries over the last 50 years. Although a number of possible explanations have been proposed to explain this trend-including increases in asthma prevalence, increases in exposure to factors that trigger asthma attacks and changes in asthma management-their relative contribution in different countries is uncertain. Another pattern is that of sudden marked increases in asthma mortality occurring in at least seven countries in the 1960s and in New Zealand in the 1970s. Available evidence indicates that the cause of these 'epidemics' was the use of high dose preparations of two specific beta-agonist drugs, namely isoprenaline forte and fenoterol. The most recent trend observed in a number of western countries during the last decade has been a gradual reduction in asthma mortality; this may relate to improvements in the management of asthma.