While procedures for approaching and recruiting men to be screened did not change from 2008 to 2011, a lower percentage of men approached in 2011 agreed to be screened than in 2008. It is possible an altruism bias (such that more altruistic MSM were more likely to participate) favored men who were more likely to be aware of their infection. However, the two samples were consistent with respect to all other variables considered and it is unlikely that such an altruism bias would greatly affect awareness and no other variable in the analysis.