Abstract: During the past two decades, the yeast Gal4 protein has been used as a model for studying transcriptional activation in eukaryotes. Many of the properties of transcriptional regulation first demonstrated for Gal4 have since been shown to be reiterated in the function of several other eukaryotic transcriptional regulators. Technological advances based on the transcriptional properties of this factor-such as the two-hybrid technology and Gal4-inducible systems for controlled gene expression-have had far-reaching influences in fields beyond transcription. In this review, we provide an updated account of Gal4 function, including data from new technologies that have been recently applied to the study of the GAL network.