The four small hsp genes of Drosophila melanogaster as well as three genes regulated during development (genes 1, 2 and 3) are localized at the chromosomal locus 67B. The four small hsp genes share strong sequence homologies between themselves which were detected here by cross-hybridization. Under the same stringency conditions, each of the genes 1, 2 and 3 hybridize to some of the small hsp genes. By DNA sequencing of gene 1, the homology was localized within the same two regions already conserved between the small hsp genes: a central region of 83 amino acids, homologous with the mammalian alpha crystallin and the first 15 N-terminal amino acids. The transcriptional inducibility of the genes 1, 2 and 3 was also compared with that of the four small hsp genes during various stages of Drosophila development at either the normal growth temperature or after a heat shock. We confirm previous reports on the developmental patterns of all seven genes and find moreover that genes 1, 2 and 3 are heat-shock inducible at any of the stages tested. We conclude that genes 1, 2 and 3 are also heat shock genes. Therefore, the locus 67B contains seven, not four, small heat shock genes.