True-false achievement test items written by typical classroom teachers show about two-thirds of the discrimination of their multiple-choice test items. This is about what should be expected in view of the higher probability of chance success on the true-false items. However, at least half again as many true-false items as multiple-choice items can be answered comfortably in the same period of time. Thus the larger number of true-false items compensates for the lower discriminating power of the individual items. The data of this study support the belief that in the hands of typical classroom teachers the two item forms can be expected to give approximately equal reliabilities for tests of equal duration. (Author)