So far this year the index is up more than 9pc.
Recent gains follow a volatile performance in 2008, a year in which the broad-based composite declined more than 19pc.
The best performing funds in May were those focused on energy and emerging markets.The HFR index for energy funds was up 9.6pc over the month, while the emerging markets index rose 9.7pc.
HFR president Kenneth Heinz said the performance represented a return in investors' risk appetite.