The Grammatical Structures Comprehension Test (CEG) has been designed to evaluate the language alterations of both Spanish speaking children and adults (specific language impairment, aphasia, craneoencephalic traumatism...) in a rapid and simple way.To study the psychometric properties of the CEG (reliability, validity and discrimination rates).The test was carried out on a sample of 1,404 children. The criteria validity was done with 181 children, whom various tests other than CEG were applied to.The discrimination rate in the 27% of the subjects with the highest scores in the CEG and the 27% of those that had the worst scores show that more than the half of the test elements produce a rate higher than 0.3 between children with good and bad scores. Out of the 20 blocks of the CEG, 15 of them present a discrimination rate between 0.5 and 1. Finally, the discrimination rate data obtained for each age group reveal that the easiest and the most difficult elements and blocks are coherently those with a lower discrimination power. This trend can be noticed in each age group.CEG is a reliable and valid measure to evaluate the grammatical comprehension, being very useful in clinics.