Regulation of inflammatory gene transcription is controlled, at least in part, by the degree of local unwinding of nucleosomal DNA. This unwinding is regulated by histone acetylation--increased acetylation results in a more loosely wound structure allowing access of basal transcription factors and RNA polymerase II. In contrast hypoacetylation of histones leads to tighter winding of DNA and reduced gene transcription. In this article we describe methods for measuring the histone acetyltransferase (HAT) and deacetylase (HDAC) activity of A549 cells. We initially describe methods examine whole cell HAT and HDAC activities and subsequently describe a technique for examining HAT activity associated with a specific co-activator CBP isolated by immunoprecipitation. These methods can also be applied to protein extracts from primary cells and from biopsy samples.