PickStock (copyright 2003, Bell Software and Services, Inc.) uses principal components analysis to search out potentially underpriced stocks by analyzing a user-supplied database of historical stock prices. The program is believed to be an implementation of what is known in the financial market modeling community as ''arbitrage pricing theory'' (see for example S. Ross, ''The arbitrage theory of capital asset pricing'', J. Economic Theory, vol. 13, pp. 341-360, 1976). The theory postulates that a given vector of prices (for example, today''s price for a set of stocks) can be explained by a linear combination of underlying economic components. While there is apparently substantial debate in the economic community as to the viability of the arbitrage pricing theory, this application provides a tool to test it out on real data.Who can best make use of this application:It is hoped that any user who can download stock price data into MetaStock text format will find PickStock sufficiently easy to use. Facility in handling text files and importing them into spreadsheets is also a plus. Economists and stock analysts may be able to utilize the program along with a more traditional analysis of economic fundamentals. Scientists, engineers, and students may even be able to tap into the powerful principal components analysis engine that PickStock incorporates by replacing closing prices with arbitrary data (ie. a given ''date'' can be associated with one experiment having outputs for each of the ''tickers'' with the output values corresponding to the ticker being in the ''close'' field).