Comparisons of mortality rates by social class bring together occupation recorded on the death certificate with data from the census. This figure shows Standardised Mortality Ratios (SMR) for deaths due to asthma in 20-64 year old men in Great Britain during 1979-80 and 1982-83 and in England and Wales during 1991-93. An SMR of less than 100 means numbers of deaths are lower than expected in that class (see LAIA factsheet 96/1 for a definition of SMR). At both times there was a trend towards higher SMRs in the manual social classes and there appears to be a widening in class differences over this period. If real, this could be due to asthma attacks being more frequent or more severe (or both) in social class V as a result of more exposure to aggravating factors or to less adequate medical care. There is no information published on women dying from asthma by social class.