Two views about the amount of opportunity available through technical education are contrasted. In popular discussions the system figures as an `alternative route' to middle class occupations. In sociological literature, however, it is dismissed as a significant source of opportunity. A review is presented of important but neglected changes in the organization of courses and the recruitment of young men to them. It is shown that both class and educational differentials do reduce the proportion of places on advanced and full time courses which are available for early leavers and for boys of working class origin. On the other hand an analysis of long run trends in terms of (i) the participation of each social class in technical education, (ii) transition rates between different levels of study, (iii) the link between qualification and occupational rewards, suggests that attempts to discount technical colleges as a source of opportunity may be premature. It is concluded that any discussion of the effect of increasing educational opportunity upon social mobility entails the examination of the institutional mechanisms through which individuals are prepared and trained for occupational roles.