Gompertzian analyses of mortality data have recently been undertaken for a number of individual conditions (Riggs JE. Mech Ageing Dev 1990; 55: 207-220 [1]; Neilson S et al. Mech Ageing Dev 1992; 64: 201-216 [2]; Neilson S et al. Acta Neurol Scand 1993; 87: 184-191 [3]). Such analyses are in principle of particular epidemiological value in circumstances where demographic change is occurring and where the balance between mortality from different conditions is subject to change. However, the extent to which a Gompertzian relationship between age and mortality holds for particular conditions has been subject to debate. In this analysis it is demonstrated that even some conditions which do not superficially hold to a Gompertz relationship do in fact do so, if such conditions are considered to be restricted to small, inherently susceptible subpopulations. By analysing mortality from a range of neurological conditions within the context of general mortality in England and Wales, conditions with different aetiologies such as Huntington's chorea, amyotrophic lateral sclerosis and multiple sclerosis can be shown to have a Gompertzian mortality rate distribution. Such analyses are of substantial value in indicating how demographic change affects the balance of mortality between conditions, as well as directing interest to revised aetiological possibilities.