In this paper, we will consider the following strongly coupled cooperative system in a spatially heterogeneous environment with Neumann boundary conditionwhere Ω is a bounded domain in R N (N 1) with smooth boundary ∂Ω; k is a positive constant, λ and μ are real constants which may be non-positive; b(x) ≡ 0 and d(x) ≡ 0 are continuous functions inΩ; ρ(x) is a smooth positive function inΩ with ∂ ν ρ(x)| ∂Ω = 0; ν is the outward unit normal vector on ∂Ω and ∂ ν = ∂/∂ν. For the case μ > 0, we show that if |μ| is small and k is large, a spatial segregation of ρ(x) and b(x) can cause the positive solution curve to form an unbounded fish-hook (⊂) shaped curve with parameter λ. For the case μ < 0, if |μ| is small and k is large, and the cooperative effect is strong for species u and very weak for species v, then the positive solution set also forms an unbounded fish-hook shaped continuum. These results are quite different from those of predator-prey systems and the cooperative system under Dirichlet boundary condition, both of which can form a bounded continuum. Our results deduce that the spatial heterogeneity of environments can produce multiple coexistence states. 1671 Our method of analysis is based on the bifurcation theory and the Lyapunov-Schmidt procedure.