Histone levels are a key factor in several nuclear processes, including transcription and chromosome segregation. Previous studies have demonstrated that Spt10 and Spt21 are required for the normal transcription of a subset of the histone genes in Saccharomyces cerevisiae, and sequence analysis has suggested that Spt10 is an acetyltransferase. We have now characterized several aspects of transcriptional activation of histone genes by Spt10 in vivo. Our results show that activation by Spt10 is dependent on its acetyltransferase domain. At HTA2-HTB2, the histone locus whose transcription is most strongly dependent on Spt10, Spt10 is physically recruited to the promoter in an Spt21-dependent and a cell cycle-dependent manner. Furthermore, Spt10 and Spt21 directly interact. These results, taken together with the identification of spt10 mutations that suppress an spt21Delta mutation, suggest a model for transcriptional activation by Spt10 and Spt21.