INTERTAIL, the computer program which implements an approach to tailored testing outlined by Cliff (1975), was examined with errorless data in several Monte Carlo studies. Three replications of each cell of a 3 x 3 table with 10, 20 and 40 items and persons were analyzed. Mean rank correlation coefficients between the true order, specified by pre-assigned random numbers, and the computed order produced by the program ranged from .93 to .99. Other efficiency measures are reported which also support the theory as a general measuring and ordering technique. Based on these results, program modifications are proposed as well as a data scheme which is to be used in further system testing. (Author)