NaturalSmalltalk is a collection of tools to analyze English texts and Smalltalk programs.This package provides scanners, stemmers, Naive Bayes classifiers, tfidfclassifiers, K-means clusterers, keyword extractor, and FastMap visualizer.Two tools, MessageSpy (profiler with keyword extraction) and WhatyaDoing(process monitor by keyword extraction) are development tools that demonstratefunctinalities of this library. NaturalSmalltalk deals with a Smalltalk code as a series of English words.For example, 'anArray at: index put: anObject' will be interpreted as'an array at index put an object'. Keyword extraction, classification, and clustering are done on this basis.