Marked deviations in the manner or content of speech. These deviations include speech that is not readily intelligible or audible; definitely unpleasant because of manner of production; deviant in rhythm, pitch or stress; or abnormal in voice, articulation or language. (Eisenson, 1965)Speech disorders are usually classified into four major groups: (a) impairments of articulation (dysarthria, cleft- palate speech); (b) defects of phonation or voice production (falsetto voice, hoarseness, raspiness, harshness etc.); (c) stuttering; and (d) language dysfunctions (delayed language, childhood and adult aphasia, baby talk, lisping, cluttering).The American Speech and Hearing Association has estimated that at least three million children in the United States are in need of remedial attention for defects of speech or impairments of hearing that affect their educational, emotional and social adjustment. This figure represents approximately 5 per cent of die total child population, and breaks down to: articulatory disorders, 3 per cent; stuttering, 1 per cent; voice, cleft-palate and cerebral palsied speech, .1 per cent each; retarded speech development, .2 per cent; and speech problems due to impaired hearing, .5 per cent. The incidence among boys is consistently higher than among girls, with some estimates running as high as three to one. Although many highly intelligent people lisp, stutter, or show other speech disorders, the over-all incidence is highest on the lower intellectual levels. At least 60 per cent of retarded children are afflicted with speech defects. There is also a higher than average incidence among children with reading difficulties, since training in reading is hampered by indistinct articulation and poor discrimination of speech sounds. Studies also show that, with important exceptions, students with defective speech tend to be somewhat retarded at all academic levels, especially those who have physical handicaps such as poor hearing. No definitive studies of the incidence of speech disorders among adults have been made.The causes of speech disorders may be either organic or functional. Among the organic conditions are: (1) severe hearing impairment, especially when it is congenital or acquired early in life; (2) cleft-palate, sometimes including cleft-lip; (3) paralysis of the speech or vocal mechanisms; (4) cerebral palsy when it involves speech mechanisms; (5) aphasias and dysarthrias resulting from neural lesions. The first four of these conditions affect both voice and articulation; dysarthria is an articulatory dysfunction; and aphasia is a loss of understanding of language due to brain damage.The functional conditions are of two general types. First, deviant patterns of speech may be acquired through imitation of the defective speech of other people. These patterns frequently improve spontaneously as the child identifies with new models in the course of his development. Second, several studies have shown that defective speech is often associated with faulty psychological patterns in the home. Among the factors most frequently emphasized are: poor adjustment on the part of the mother; maternal tendencies toward overprotectiveness, rigidity, restrictiveness and domination through excessively high standards and adverse criticism; and a home environment characterized by disorganization and tension. (Wood, 1946, Peckarsky, 1952, Moncur, 1952)Discussion of individual speech disorders is found under the following topics: STUTTERING, CLUTTERING, DYS- LALIA, DYSARTHRIA, APHASIA, JARGONLALIA, PARAPHASIA, VERBIGERATION, LOO- ORRHEA, WORD SALAD.