Many years ago it was pointed out by Holbourn (1936) that there is an apparent breakdown on angular momentum conservation on reflection of circularly polarised light. The author points out that the discrepancy may be resolved by considering transverse positional shifts on reflection as described by Schilling (1965), Imbert (1972) and subsequent authors, and examines the values of the shifts necessary to satisfy angular momentum conservation in various situations. It is found that shifts satisfactory in this respect may be obtained by use of a fairly general phase-shift argument-similar in formalism to that used by Julia and Neveu (1973)-at least for the case of total reflection. However, the situation is less satisfactory for partial reflection, nor is it clear that the shift values, even for the case of total reflection, agree with those measured by Imbert and others, or calculated numerically as by Ashby and Miller (1976) for instance. It is suggested that further experimental work may be useful in clarifying the situation.