The Arabidopsis thaliana SPL gene family represents a group of structurally diverse genes encoding putative transcription factors found apparently only in plants. The distinguishing characteristic of the SPL gene family is the SBP-box encoding a conserved protein domain of 76 amino acids in length, the SBP-domain, which is responsible for the interaction with DNA. We present here characterisation of 12 members of the SPL gene family. These genes show highly diverse genomic organisations and are found scattered over the Arabidopsis genome. Some SPL genes are constitutively expressed, while transcriptional activity of others is under developmental control. Based on phylogenetic reconstruction, gene structure and expression patterns, they can be divided into subfamilies. In addition to the Arabidopsis SPL genes, we isolated and determined the sequences of three SBP-box genes from Antirrhinum majus and seven from Zea mays.