This study aims to answer the question, how much of Spanish Sign Language interpreting deaf individuals really understand. Study sampling included 36 deaf people (deafness ranging from severe to profound; variety depending on the age at which they learned sign language) and 36 hearing people who had good knowledge of sign language (most were interpreters). Sign language comprehension was assessed using passages of secondary level. After being exposed to the passages, the participants had to tell what they had understood about them, answer a set of related questions, and offer a title for the passage. Sign language comprehension by deaf participants was quite acceptable but not as good as that by hearing signers who, unlike deaf participants, were not only late learners of sign language as a second language but had also learned it through formal training.