INFORMATION WAS OBTAINED CONCERNING BASIC LEARNING CHARACTERISTICS OF RETARDED CHILDREN USING, INSOFAR AS POSSIBLE, MATERIALS WITH WHICH THEY HAVE HAD LITTLE OR NO PREVIOUS FAMILIARITY. THIRTY MENTALLY RETARDED AND AN EQUAL NUMBER OF NORMAL CHILDREN RANGING FROM 8 TO 9 YEARS IN MENTAL AGE WERE THE SUBJECTS OF THE STUDY. STANDARDIZED LISTS OF NONSENSE SYLLABLES, TESTS INVOLVING CANCELLATION OF SELECTED NUMBERS IN A SERIES OF SIX-PLACE NUMBERS, ASSEMBLY TASKS, AND OBJECT, PICTURE, AND WORD PROBLEMS OF REASONING, WERE GIVEN TO EACH SUBJECT. THE DATA WERE ANALYZED THROUGH STANDARD STATISTICAL ANALYSES OF DIFFERENCES BETWEEN GROUPS, AND INDIVIDUAL DATA SHEETS WERE ANALYZED AND CHARTED TO NOTE INDIVIDUAL SIMILARITIES AND DIFFERENCES. IT WAS CONCLUDED THAT THE LEARNING RATE OF MENTALLY HANDICAPPED CHILDREN IS AT LEAST EQUAL TO THAT OF NORMAL CHILDREN OF THE SAME MENTAL AGE OR DEVELOPMENTAL LEVEL. THUS A GROUP OF MENTALLY HANDICAPPED CHILDREN WILL BE ABLE TO LEARN SPECIFIC SKILLS AT THAT DEVELOPMENTAL LEVEL AT LEAST EQUALLY WELL AND WITH EQUAL RAPIDITY. HOWEVER, IT WILL TAKE THE MENTALLY HANDICAPPED GROUP APPROXIMATELY 1-1/2 YEARS TO DEVELOP INTELLECTUALLY THE SAME AMOUNT NORMAL CHILDREN WILL DEVELOP IN 1 YEAR. THE PRESENT SERIES OF STUDIES WAS LARGELY THEORETICAL IN NATURE AND SHOULD BE FOLLOWED UP WITH A PARALLEL SERIES CONCERNED WITH TASKS INVOLVING ACADEMIC LEARNING. (GC)