Optimizing compilers typically limit the scope of their analyses and optimizations to individual modules. This has two drawbacks: first, library code cannot be optimized together with their callers, which implies that reusing code through libraries incurs a penalty; and second, the results of analysis and optimization cannot be propagated from an application module written in one language to a module written in another. A possible solution is to carry out (additional) program optimization at link time. This paper describes our experiences with such optimization using three different optimizing Scheme compilers, and several benchmark programs, via alto, a link-time optimizer we have developed for the DEC Alpha architecture. Experiments indicate that significant performance improvements are possible via link-time optimization even when the input programs have already been subjected to high levels of compile-time optimization.