Objective To measure sexual mixing among racial groups of men who have sex with men (MSM).

Methods The authors explore its potential impacts, making two methodological advancements over previous work. First, the authors pioneer the use of Newman's assortativity coefficient to characterise mixing among MSM. Second, the authors examine mixing at the level of primary ties and at the level of secondary ties.

Results Results from the 1142-participant sample suggest that MSM are highly assortative by all races at the secondary level.

Conclusions Networks of MSM may be more tightly contracted around racial groupings than previously supposed. These groupings may lead to increased HIV transmission in certain racial groups.