A subset A of a given finite abelian group G is called (k, l)-sum-free if the sum of k (not necessarily distinct) elements of A does not equal the sum of l (not necessarily distinct) elements of A. We are interested in finding the maximum size λ k,l (G) of a (k, l)-sum-free subset in G.A (2, 1)-sum-free set is simply called a sum-free set. The maximum size of a sum-free set in the cyclic group Zn was found almost forty years ago by Diamanda and Yap; the general case for arbitrary finite abelian groups was recently settled by Green and Ruzsa. Here we find the value of λ3,1(Zn). More generally, a recent paper of Hamidoune and Plagne examines (k, l)-sum-free sets in G when k − l and the order of G are relatively prime; we extend their results to see what happens without this assumption.