Many thanks to William Hart, Ted Snowdown, Michel Camus and Henry Silvert on the subject of using income quintiles versus income quartiles when studying social class. Very useful comments where made on: a) differences between social class and socio-economic status b) country-specificity of social class and socio-economic status c) the problem of approaching socio-economic status being one of content more than scale. d) useful references an ons.ac.uk Carlos Matias Dias Centro de Epidemiologia e Bioestatística Observatório Nacional de Saúde Instituto Nacional de Saúde Dr. Ricardo Jorge Av. Padre Cruz 1699 Lisboa codex Portugal Telef: + 01 7510535 Fax: + 01 7573671 Correio electrónico: [log in to unmask] %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%