During the past year, there have been rapid advances in our understanding of the early events of T-cell development, at the molecular level. Studies at the transcriptional level of T-cell receptor gene regulation have started to yield important clues about how different T-cell-specific genes can share the same transcription factors and how αß and γδ T cells are differentially regulated. In addition, studies using transgenic mice with the T-cell receptor γδ genes have further strengthened the separate lineage model of αß and γδ T cells and brought into play the importance of negative cis-regulatory elements for lineage-specific determination.