Given the high quality of the output of the Nuffield Social Mobility Group, critical comments must be made with due caution. However, despite the fact that the article by Goldthorpe and Llewellyn, 'Class Mobility in Modern Britain', Sociology, vol. n, no. 2, is methodologically rigorous and closely argued, the extent to which existing mobility data can be utilized in the analysis of the class structure of contemporary Britain may still be questioned. However, it should be stressed that these comments focus on the appropriateness of current mobility studies for class analysis, and should not be interpreted as challenging the value of these studies which have provided much-needed empirical data in a more general sense. Goldthorpe and Llewellyn correctly argue that questions of social mobility are highly relevant to recent neo-Weberian class theories.2 That is, 'mobility chances', as a vital element in 'life chances', crucially delineate the 'classes' so identified. However, for the purposes of class analysis, a drawback of most survey inquiries into mobility since the Second World War is that they 'have been conducted in terms of hierarchies of prestige or socioeconomic status rather than of class' (p. 257). Accordingly, Goldthorpe and Llewellyn construct a sevenfold schema of class positions using the 36-category version of the HopeGoldthorpe occupational scale. This schema brings together groups of occupations whose 'incumbents will typically share in broadly similar market and work situations which, following Lockwood's well-known discussion, we take as the two major components of class position' (p. 259 emphasis in original). As the schema is representative of social classes , rather than being a hierarchy of occupational prestige or socio-economic status, they emphasize that '. . . the schema should not be regarded as having nor should it be expected to have a consistently hierarchical form' (p. 260). Nevertheless, when they later present their fascinating data on 'work-life' mobility, the sevenfold class schema is collapsed into a threefold hierarchy, and utilized as such. (Classes 1 and 2 are grouped together, followed by 3, 4, and 5, then 6 and 7). In principle such a procedure is not objectionable. Given the concepts employed in the identification of class positions i.e. 'market' and 'work' situations it is clearly possible to rank occupations as 'better' or 'worse' in these respects. However, a comparison of the threefold class hierarchy with the 36 categories of the original Hope-Goldthorpe scale reveals the possibility of some rather odd cases of upward (or conversely downward) mobility.3 For example, a move, say, from machine setter or printer (H-G category 22, Class 6 on the sevenfold scale) to a caretaker, doorman, (H-G category 34, Class 3 on the sevenfold scale), or shop salesman (HG category 28, Class 3 on the sevenfold scale), would be characterized as 'upward' class mobility. I would suggest that, in terms of 'market' and 'work' situations, the description of such moves as 'upward' is doubtful. Empirical evidence presented by Goldthorpe and Llewellyn demonstrates that both the amount and range of social mobility experienced by their sample of over ten thousand is such as to challenge a number of theses generated by neo-Weberian class theory. These theses include 'closure' (the restriction of mobility at the upper and lower levels of the occupational hierarchy); the 'buffer zone' (mobility as primarily short-range movement