The presentation of genetic diseases in French secondary school biology textbooks is analysed to determine the major conceptions taught in the field of human genetics. References to genetic diseases, and the processes by which they are explained (monogeny, polygeny, chromosomal anomaly and environmental influence) are studied in recent French text-books targeted at the four different school levels for students between the ages of 15 and 18. Four different publishers' textbooks are included per school level. It is found that direct, linear and causal genetic determinism is the interpretative model most often associated with genetic diseases. Nevertheless, environmental influences are more often addressed in recent textbooks than in older ones, and are mainly associated with polygenic models of genetic determinism. The issues surrounding these results are discussed. (Contains 3 figures and 5 tables.)