Avant-propos/Foreword. Biostatistics and epidemiology: measuring the risk attribuable to an environmental or genetic factor. Coronary heart disease aetiology: associations and causality. Progress in the epidemiological understanding of geneenvironment interactions in major diseases: cancer. Interaction between genes and environment in neurodegenerative diseases. Geneenvironment interactions in addictive disorders: epidemiological and methodological aspects. Studies of fertility and fecundity: comparative approaches from demography and epidemiology. Observation versus intervention in the evaluation of drugs: the story of hormone replacement therapy. The perpetuation and epidemic recurrence of communicable diseases in human populations. Epidemic modeling in complex realities.