Game theory has had remarkable success as a framework for the discussi
on of animal behaviour and evolution. It suggested new interpretations
and prompted new observational studies. Most of this work has been do
ne with 2-player games. That is the individuals of a population compet
e in pairwise interactions. While this is often the case in nature, it
is not exclusively so. Here we introduce a class of models for situat
ions in which more than two (possibly very many) individuals compete s
imultaneously. It is shown that the solutions (i.e. the behaviour whic
h may be expected to be observable for long periods) are more complex
than for 2-player games. The concluding section lists some of the new
phenomena which can occur. (C) 1997 Society for Mathematical Biology.