Variational problems under uniform quasiconvex constraints on the gradient are studied. In particular, existence of solutions to such problems is proved as well as existence of lagrange multipliers associated to the uniform constraint. They are shown to satisfy an Euler-Lagrange equation and a complementarity property. Our technique consists in approximating the original problem by a one-parameter family of smooth unconstrained optimization problems. Numerical experiments confirm the ability of our method to accurately compute solutions and Lagrange multipliers. 2. Statement of the problem and main results. Let Ω be a bounded domain in R N with N ≥ 1 and T : Ω × R m×N → [0, ∞[ a Carathéodory function. Let s ≥ 1 and consider a functional J : W 1,s (Ω; R m ) → R ∪ {+∞}, which is supposed to be bounded from below and sequentially lower semicontinuous in the weak topology of W 1,s (Ω; R m ). We are interested in the minimization problem inf{J(v) | T (·, ∇v) ∞,Ω ≤ 1, v ∈ g + W 1,s 0 (Ω; R m )}, (2.1)where T (·, ∇v) ∞,Ω = ess-sup{T (x, ∇v(x)) | x ∈ Ω}, and g ∈ W 1,∞ (Ω; R m ) ∩ C(Ω; R m ) is a given function satisfying J(g) < +∞ and T (x, ∇g(x)) ≤ 1 for a.e. x ∈ Ω.Then (2.1) may be rewritten as inf J ∞ (v) | v ∈ g + W 1,s 0 (Ω; R m ) .(2.3)