Bebbington (1986) draws attention to a possible cause for concern regarding the comparability of recent epidemiological research utilising the PSE-ID-CATEGO system of psychiatric caseness deter mination. In taking issue with our observation that cases in our recent community survey (Brown et al, 1985) were broadly similar in terms of severity to those reported in a recent series of out-patients (Sashidharan, 1985), he makes the point that such conclusions are only justifiable when it can be con fidently assumed that thresholds for symptom in clusion are applied uniformly between research centres. He argues that this assumption may well be invalid and marshalls two arguments to suggest that the Bedford team may have adopted less stringent rating thresholds. Firstly, he draws attention to the very different population prevalences of disorder reported in recent surveys, contrasting one-year prevalence figures for the Bedford College survey in Islington (Brown elal, 1985) withthelowerrates reported for other investigations in Edinburgh (Dean eta!, 1983) and Camberwell (Bebbington et al, 1981). Secondly, he reminds us of the body of evidence which suggests that psychiatrists operate stricter criteria for PSE symptoms than their lay colleagues (Wing et al, 1977a; Sturt et al, 1981).