The relationship of time spent in either Montessori or traditional preschool programs to the preschooler's development in five parameters was studied. The five parameters were: (1) personal skills; (2) relationship with teachers; (3) peer relations; (4) behavioral control; and (5) cognitive skills. A review of the literature on Montessori and other preschool programs is presented. Three Montessori programs and three traditional programs provided the subjects for the study. The Prekindergarten Scale, a multiple choice behavioral rating scale, was completed for each child by the program teachers. Results revealed that the only significant variable for predicting time in program for the traditional program was relationship with teachers, which was also the only variable that was insignificant in predicting time in program for the Montessori program. The strongest relationship was between time in the Montessori program and relationship with peers with age controlled. Four tables of quantitative data used in the study and 12 references are appended. (GLR)