The ARnoldi PACKage is a library of routines capable of solving large scale symmetric, nonsymmetric, and generalized eigenproblems. The software is designed to compute a few eigenvalues with user specified features such as those of largest real part or largest magnitude. Storage requirements are on the order of n*k locations. No auxiliary storage is required. A set of Schur basis vectors for the desired k-dimensional eigen-space is computed which is numerically orthogonal to working precision. Numerically accurate eigenvectors are available on request.