Abstract
In this paper we study the order of Runge-Kutta methods applied to differential-algebraic equations of index one. We derive general order conditions for the local order k L {k_L} , and give a convergence result, which shows that the order k G {k_G} of the global error satisfies k G ≥ k L − 1 {k_G} \geq {k_L} - 1 . We also describe some numerical experiments, which are in agreement with our results.