A set of stcok option pricing models are implemented on the connection Machine-2 and the DECmpp-1200 to compare model prices and historical market data. improved models, which incoporate stochastic volatility with American call generally have smaller pricing errors than simpler models which are based on constrant volalility and European call. In a refinement of the comparison between model and market prices, a figure of merit based on the bid / ask spread in the market, and the use of optimization techniques fo rmodel parameter estimation, are evaluted. Optimization appears to hold great promise for improving the accuracy of existing pricing models, espicially for stocks which are difficult to price with conventional models.