Significant changes have occurred in the distribution of trout in streams of Great Smoky Mountains National Park since 1900. By the mid-1970's the original range of the native brook trout had been reduced by about 70% and the species was relegated to suboptimal habitat in head water streams. Most of the stream sections lost by brook trout became the territory of the introduced rainbow trout, which in 1977 occupied about 80% of the Park waters. After 1950, brown trout introduced in State waters outside the Park established reproducing populations in some 50 miles of stream formerly occupied only by rainbow trout. If current trends continue, the recovery of brook trout in Park water may be difficult, if not impossible, and brown trout may occupy much of the territory now held by rainbow trout.