A word problem is more difficult to solve when the minimum number of different operations to reach the correct solution is large, when it is of a different type than a problem preceding it, when the indexed complexity of its most complex sentence is great, when there are a large number of words in the problem, and when a conversion of units (as from days to weeks) is required. These variables of problem difficulty were determined to be significant in an experiment using 16 disadvantaged sixth-grade students, who were given access to a computer-based teletype. Variables that did not make a significant contribution to the regression analysis were: the "verbal-clue" variable, the "order" variable, and the "steps" variable. (MF)