Abstract: The general transcription factor TFIID is composed of the TATA box binding protein (TBP) and a set of conserved TBP-associated factors (TAFs). Here we report the completion of genome-wide expression profiling analyses of yeast strains bearing temperature-sensitive mutations in each of the 13 essential TAFs. The percentage of the yeast genome dependent on each TAF ranges from 3% (TAF2) to 59-61% (TAF9). Approximately 84% of yeast genes are dependent upon one or more TAFs and 16% of yeast genes are TAF independent. In addition, this complete analysis defines three distinct classes of yeast promoters whose transcriptional requirements for TAFs differ substantially. Using this collection of temperature-sensitive mutants, we show that in all cases the transcriptional dependence for a TAF can be explained by a requirement for TBP recruitment and assembly of the preinitiation complex (PIC). Unexpectedly, these assembly experiments reveal that TAF11 and TAF13 appear to provide the critical functional contacts with TBP during PIC assembly. Collectively, our results confirm and extend the proposal that individual TAFs have selective transcriptional roles and distinct functions.