To study how the E1A polypeptides of adenovirus type 2 regulate transcription, we have constructed chimeric plasmids containing the bacterial gene encoding chloramphenicol acetyl transferase (CAT) under the control of either the wild type or the deleted E4 promoter of adenovirus type 2. Our previous results showed that promoter sequences located upstream from position -158, as measured from the cap site, are essential to the transactivation process. From a new set of deletion mutants, we now show that two regions, located between positions -239 and -218 and between positions -179 and -158, are involved in the E1A transactivation process. The deletion of only one of them does not significantly alter the E1A induction process compared with the wild type. Moreover, we show that these two regions lie within a DNA fragment which possesses the properties of an E1A-inducible "enhancer-like" element. In addition, the DNA fragment which contains this enhancer element is also able to confer the E1A inducibility to a heterologous promoter.