Reptiles occupy a key position in the evolution of terrestrial vertebrates. Their evolutionary history is well known, they show a wide morphological and ecological variety, and they have a particularly complex system of sex differentiation, ranging from strict genetic determination with or without differentiated sex chromosomes to strict thermal determination. This thematic issue presents diverse facets of reptilian cytogenetics and genomics including - a study of the genome structure based on the analysis of two proto-oncogenes - the existence and evolution of transposable elements - the role of molecular and chromosomal variations in phylogenetic processes - a study of chromosome composition through isolation of specific sequences and chromosome painting - the involvement of chromosomes in sex determination and the coevolutionary interaction between sex chromosomes, genome organization and temperature - the hybrid origin of parthenogenetic lizards Providing an up-to-date overview of what is currently known about molecular cytogenetics, genome organization and evolution in reptiles, this publication will be of interest to researchers in the fields of cell biology, cytogenetics, genetics, molecular biology, molecular evolution, phylogenesis and zoology.