Histone acetylation is one major mechanism by which chromatin structure and function are regulated. Besides histones, many nonhistone proteins are also acetylated in vivo. Aberrant acetylation has been linked to the development of various human diseases. Through acetylating histone and nonhistone proteins, histone acetyltransferases (HATs) play fundamental roles in regulating chromatin remodeling, transcription, and other nuclear processes. Known HATs belong to several groups, including the GCN5/PCAF, p300/CBP, and MYST families. ESA1, SAS3, MOF, TIP60, HBO1, MOZ, and MORF are the MYST family members with demonstrated HAT activity. The MOZ and MORF genes are rearranged by chromosome abnormalities associated with several types of leukemia, so these two HATs have been implicated in leukemogenesis. Compared with p300, CBP, and PCAF, much less is known about MOZ and MORF. To elucidate the function and regulation of these two interesting HATs, we have conducted their initial characterization. Here we describe the expression, purification, and activity analysis of MOZ and MORF. For comparison, we also include the procedure for expression and purification of PCAF. These methods are useful not only for functional characterization of MOZ, MORF, PCAF, and other HATs, but also for preparation of HAT proteins to screen compound libraries and obtain inhibitors with potential therapeutic value.