THE FACTORS RELATED TO UNDERACHIEVEMENT AND LOW ACHIEVEMENT IN MATHEMATICS LEARNING WERE STUDIED. USING AN INDIVIDUAL CLINICAL APPROACH, THE STUDY WAS CONDUCTED WITH TWO SAMPLE GROUPS, 12 UNDERACHIEVERS AND 11 LOW ACHIEVERS, IN GRADES 4-6. SCORES WERE OBTAINED ON CONCRETE, SEMICONCRETE, AND ABSTRACT REASONING LEVELS FOR THE MATHEMATICS EDUCATION AREAS OF LINEAR MEASUREMENT AND PLACE VALUE. ADDITIONAL EVALUATIVE DATA, BOTH OBJECTIVE AND SUBJECTIVE, WERE COLLECTED THROUGH INTENSIVE CASE STUDIES ON EACH STUDENT. NO CONSISTENT PATTERN WAS FOUND FOR EITHER GROUP IN ABILITIES TO FUNCTION ON THE THREE DIFFERENT LEVELS OF REASONING. SEVERAL DIFFERENCES, HOWEVER, WERE FOUND BETWEEN THE TWO GROUPS WHEN EVALUATIVE DATA ON THEIR HOME ENVIRONMENTS AND SOCIAL ADJUSTMENTS WERE COMPARED. PROJECT RECOMMENDATIONS WERE BASED ON THOSE DIFFERENCES--(1) LOW ACHIEVERS NEED TO BE EXPOSED TO COMPREHENSIVE COUNSELING AND REMEDIAL PROGRAMS BASED ON THEIR INDIVIDUAL LEVELS OF ABSTRACTIVE ABILITY, AND (2) UNDERACHIEVERS SHOULD PARTICIPATE IN SPECIAL PROGRAMS DESIGNED TO REDUCE ANXIETY TOWARD MATHEMATICS. (JH)