Thirty four Puertorrican, ages 8 to 10 years old from two different socioeconomic groups were tested to compare their scores in both WISC and WISC-R. The tests were administered in a counterbalanced order with a test-retested interval of one week. Significant WISC/WISC-R differences were found with the WISC-R yielding lower results in all 3 scales and in some subtests. These results have very important implications for the assessment of the intelligence of the children of Puerto Rico, since more children might be injustly diagnosed as Mentally Retarded.