In preschoolers, disorders of higher cerebral function are most likely to present as inadequate development of language, while in school-age children, learning disabilities and attention deficit predominate. The main considerations in the differential diagnosis in preschoolers with inadequate language are hearing loss, mental deficiency, dysphasia, and autistic spectrum disorders. Attention to the child's ability to engage in symbolic play and communicate meaningfully is the key to this often baffling differential diagnosis. With the exception of definitive assessment of hearing, classic medical investigations are seldom informative because structural brain lesions and metabolic errors are much rarer etiologies than prenatal and genetic influences on brain development. While many children improve with age, the underlying deficit(s) usually persists. The role of the physician is to detect the developmental problem, give the parents a correct diagnosis, refer the child for appropriate investigation and intervention, and provide follow-up and counseling. Early diagnosis is essential for effective remediation.