This paper is concerned with segregation and school selectivity in secondary schools with a religious character in London, England. Analyses of the characteristics of pupils at religious and non-religious schools reveal that the former tend to cater predominantly for pupils from particular religions and/or denominations and ethnic groups, so fostering segregation. In addition, they educate, in the main, pupils who are from more affluent backgrounds and with higher levels of prior attainment than pupils in non-religious schools. Moreover, the evidence suggests that some "elite" secondary schools are "selecting in" and "selecting out" particular pupils. A range of different admissions criteria and practices are identified which appear to foster school selectivity. It is argued that there may have been a distortion of mission for at least some religious schools given that they were originally set up to educate the poor. Implications for policy are discussed. (Contains 6 figures, 9 tables and 10 notes.)