Motor neuron disease (MND) mortality rates are rising in Europe and the USA. The most comprehensive UK study was conducted more than 15 years ago. This study examines trends in mortality from MND in England & Wales, and Scotland, between 1975 and 2004. Age, gender, and cause-specific mortality rates were calculated for the period 1975-2004 using national data from England & Wales, and Scotland. Rates were directly age-standardized to the European standard population. Trends in mortality rates over time were examined for men and women separately, as well as by the age groups 0-59 years, and 60 or more years. MND mortality rates rose steadily over the 30-year period 1975-2004 in both sexes in England & Wales, and Scotland. There is a clear upward trend in all four groups (p for trend <0.001). All increases were largely restricted to the age group 60 years and above, with rates showing increases of 70-80%, and no evidence of a flattening of this trajectory. Rates for the 0-59 years age group remained stable over the period. There is evidence of a narrowing of the male-female gap in mortality rates for the age group over 60 years in England and Wales.