Since the 1960s, the methodology recommended by the International Commission on Radiological Protection (ICRP) for assessment of individual doses has developed significantly, yet the specific recommendations related to the characteristics of 'critical groups' for the purposes of protection of the public have been interpreted but are relatively unchanged. This paper examines developments relevant to the criteria for appropriate homogeneity of habits within critical groups. It is suggested that, with the need for additivity of effective doses summed over different contributing exposure pathways, an important criterion for selection of the critical group is homogeneity of summed effective doses rather than, necessarily, of the underlying factors such as ages and habits focusing on a particular pathway. This implies that there need be less emphasis than before on the term 'critical pathway'. However, examples of recent retrospective assessments near UK nuclear establishments are given and it is shown that, in practice, critical groups selected on the basis of summed effective doses are still fairly homogeneous in terms of detailed habits.