Following a literature review on speech and language development of twins, case studies are presented of six sets of identical twins screened for entrance into kindergarten. Five sets of the twins and one boy from the sixth set failed to pass the screening test, particularly the speech and language section, and were referred for therapy to correct articulation and/or language delays. Conclusions drawn from the research review and case studies include: (1) identical twins tend to have delays in speech and language development; (2) speech and language problems typically include articulation disorders, low vocabulary scores, delays in expressive and receptive language skills, stuttering, and a secret "twin talk" (idioglossia); (3) speech/language development does not seem to be affected by birth history, birth order, nursery school experience, or educational background of the parents; (4) twin boys seem to have more speech and language delays than twin girls; (5) twins who develop "twin talk" are those who are rarely separated; and (6) the earlier that speech and language delays are identified, the better the chances of successful treatment. The paper contains a twin questionnaire for mothers and concludes with guidelines for parents to determine their child's level of language development and suggestions for improving language skills. Two charts for use as guides to speech and language development are included. (JDD)