The purpose of this study was to investigate the length development of the sign language sentences which Korean deaf students began to learn after entering the schools for the hearing impairments. For this purpose, the samples of sign language scenes from 66 deaf students, who were selected by 6 students(3 male and 3 female) of each grade ranging from the 2nd grade of the elementary to the 3rd grade of the senior high course in schools for the hearing impairments, were recorded on viedeo tape and analyzed. The results can be summarized as follows. The lengthes of the sign language sentences increased according to the advance of the grade level. The length of the sign language sentence developed rapidly in the high-grades of elementary course, but did slowly after that time. The length of the sign language sentences most frquently appeared was 1 to 3 words in the low-grades of elementary course, 1 to 6 words in the high-grades of elementary and junior high course, and 4 to 9 words in the senior high course ,respectively. The mean lengths of words were 1.16 in the low-grades of elementary course, 4.18 in the high-grades of elementary course, 4.62 in the junior high course, and 6.10 in the senior high course, respectively. The length development of the sign language sentences with the deaf students is later than that of Korean language sentences with the hearing students. But the reason is thought, not to be that the deaf students are more retarded than the hearing students, but to be that the deaf students\'age exposed to the sign language is later.