We consider a system of nonlinear Schrödinger equations with periodic boundary conditions of the form
i ∂uj/∂t + D2uj = −fj (u, ū), t ≥ 0, x ∈ (−2,2),
uj (0, x) = uj0(x), x ∈ (−2,2),
Dkuj (t, −2) = Dkuj (t, 2), t ≥ 0, k = 0, 1,
where D = ∂/∂x, j = 1,..., m, fj (u, ū) = ∂g(u, ū)/∂ū, and ∂g/∂uj = –f j for some homogenous function g(u, ū) such that g(λu, λū) = λ6g(u, ū). We obtain sufficient conditions for blow-up of solutions of this system in C1([0,t0);H2(−2,2)).