The Fisher Exact Probability Test considers independent groups and dichotomous criterion in a 2 by 2 (fourfold) contingency table. Fisher's test requires a determination of the combined probability of the observed frequency distribution and of the more extreme (in the same direction) frequency distributions. Typically, Fisher's test is for a small sample, with a total size of 30 or less. Otherwise, the computations required are much too tedious, and chi-square is used. This paper presents a mathematical discussion as well as a computer program for Fisher's test. Included are usage instructions and an illustrative problem. Depending on the frequency pattern, this program can handle sample sizes of about 500. Therefore, in most instances, a researcher does not have to resort to approximation methods. (Author)