Although a vast inventory of morphological mutants of Arabidopsis thaliana is available, only some have been used for genetic studies of leaf development. Such is the case with the Arabidopsis Information Service (AIS) Form Mutants collection, assembled by A. R. Kranz and currently stored at the Nottingham Arabidopsis Stock Centre, which includes a large number of mutant lines, most of which have been little studied. With the aim of contributing to the genetic dissection of leaf ontogeny, we have subjected 57 mutant lines isolated by others to genetic analysis; 47 of which were from the AIS collection. These are characterized by vegetative leaves of abnormal shape or size, and were chosen as candidates for mutations in genes required for leaf morphogenesis. The mutant phenotypes studied were shown to be inherited as single recessive Mendelian traits and were classified into 10 phenotypic classes. These mutant strains were found to fall into 37 complementation groups, 7 of which corresponded to known genes. Results of the phenotypic analysis and data on the genetic interactions of these mutants are presented, and their possible developmental defects discussed.