The Standard Template Adaptive Parallel Library (STAPL) is a parallel library designed as a superset of the ANSI C++ Standard Template Library (STL). It is sequentially consistent for functions with the same name, and executes on uni- or multi-processor systems that utilize shared or distributed memory. STAPL is implemented using simple parallel extensions of C++ that currently provide a SPMD model of parallelism, and supports nested parallelism. The library is intended to be general purpose, but emphasizes irregular programs to allow the exploitation of parallelism in areas such as particle transport calculations, molecular dynamics, geometric modeling, and graph algorithms, which use dynamically linked data structures. STAPL provides several different algorithms for some library routines, and selects among them adaptively at run-time. STAPL can replace STL automatically by invoking a preprocessing translation phase. The performance of translated code is close to the results obtained using STAPL directly (less than 5% performance deterioration). However, STAPL also provides functionality to allow the user to further optimize the code and achieve additional performance gains. We present results obtained using STAPL for a molecular dynamics code and a particle transport code.