PVODE is a solver for large systems of ordinary differential equations on parallel machines. It contains methods for the solution of both stiff and non-stiff initial value problems. Integration methods include the variable coefficient forms of the Adams and Backward Differentiation Formula methods. The linear systems that must be solved during the implicit time stepping are solved with iterative, preconditioned Krylov solvers. The user can either supply a preconditioner or use one that is included in the PVODE package. PVODE is an extension of the sequential package known as CVODE which has been widely distributed and used. CVODE is available from Netlib. Both PVODE and CVODE are written in C but are callable from Fortran. The parallelization of CVODE to PVODE was accomplished through the modification of the vector kernels, allowing them to operate on vectors that have been distributed across processors. The message passing calls are made through MPI.