Naira is a compiler for Haskell, written in Glasgow parallel Haskell. It exhibits modest, but irregular, parallelism that is determined by properties of the program being compiled, e.g. the complexity of the types and of the pattern matching. We report four experiments into Naira's parallel behaviour using a set of realistic inputs: namely the 18 Haskell modules of Naira itself. The issues investigated are: Does increasing input size improve sequential efficiency and speedup? To what extent do high communications latencies reduce average parallelism and speedup? Does migrating running threads between processors improve average parallelism and speedup at all latencies? © 2002 Published by Elsevier Science Inc.