The purpose of this study was to compare the performance of ninth-grade slow readers with ninth-grade good readers and with sixth grade readers on a test of syntactic comprehension. The significant difference between the ninth-grade good readers' and the ninth-grade slow readers' performance on A Test of Sentence Meaning (ATSM), developed by Albert D. Marcus, clearly shows that comprehension of syntactic structure is an element in total reading comprehension. The low correlation between the total reading scores and the ATSM score would seem to indicate that it is not an important factor in reading at this level. The correlation of .70 between reading and the ATSM indicates that comprehension of syntactic structures is an important reading factor for sixth grade readers even on a survey reading test. It is suggested that the great difference in the correlations between the sixth-grade readers and the ninth-grade readers indicates that although these two groups measure on The Nelson Reading Test to be very similar with the same range and almost the same means, they must differ in at least one important respect. (LL)