A continuation of the field test of Developing Mathematical Processes (DMP) was conducted in eight schools. Four were multiunit schools located in settings ranging from small town to large city; the remaining schools were conventionally organized and located in large urban areas. The purpose of the field test was (1) to determine the effectiveness of the instructional program in terms of student achievement, and (2) to document the usability of the program. The field test focused on the third level of the program. The results indicated a mastery level of approximately 81 percent on the specific objectives of the program. Overall performance was retarded by poor results in one topic. On the latter portions of the program, maintenance of the mastery level reached a level of 83 percent. The data on standardized test achievement did not conclusively favor either DMP or its conventional counterparts. The field test established that (1) teachers will expend the effort to attend frequent inservice meetings, to prepare instructional materials, and to plan for the several instructional modes in the program; and (2) students will enthusiantically participate in the learning activities. On the basis of the data gathered in the field test, DMP was demonstrated to be a viable program for second-grade children. (Author/SD)