The relation of short-term memory to sentence comprehension was investigated in 4 children who had sustained severe closed head injury. Two of the patients showed dissociation in performance on short term memory tasks. One of the patients, CS showed a pattern of performance on short term memory tasks consistent with a phonological short term memory deficit. Another patient, CB, showed a pattern of performance which suggests a deficit in semantic memory. The dissociations in short term memory tasks exhibited by these patients corresponded to a dissociation in their performance on sentence processing tasks. On a sentence anomaly judgment task in which the memory load had to be maintained before the judgment could be made CS performed similarly to the Control subjects, while CB showed a deficit which was related to memory load. The opposite pattern was observed for a verbatim sentence repetition task on which CB's performance was within the normal range, but CS was very impaired. The results support models of short term memory that postulate separable components of semantic and phonological short term memory and the differential contribution of the two components to sentence comprehension.