This ancillary study to SMART will use relevant data and specimens from three subsamples of SMART participants and key subgroups. The three subsamples include participants randomly assigned to episodic or continuous ART, participants who had no previous use of ART prior to study entry or had ceased ART within 6 months prior to study entry, and participants who had experienced a CVD event with two matched controls for each case. The subgroups will include episodic and continuous ART participants who were taking either a protease inhibitor (PI) or non-nucleoside reverse transcriptase inhibitor (NNRTI) at study entry.