Saccharomyces cerevisiaecells control their cell size at a point in late G1 called Start. Here, we describe a negative role for the Sin3⁄Rpd3 histone deacetylase complex in the regulation of cell size at Start. Initiation of G1 ⁄S-specific transcription ofCLN1, CLN2andPCL1in a sin3Dstrain occurs at a reduced cell size compared with a wild-type strain.