The characteristics of various genetic syndromes have included "stuttering" as a primary symptom associated with that syndrome. Specifically, Down syndrome, fragile X syndrome, Prader-Willi syndrome, Tourette syndrome, Neurofibromatosis type I, and Turner syndrome all list "stuttering" as a characteristic of that syndrome. An extensive review of these syndromes indicated clients diagnosed with these syndromes do show evidence of nonfluency patterns, but not all would be considered stuttering. Many of the syndromes are marked by degrees of mental retardation that probably contribute to a higher than average prevalence of stuttering, as well as a higher than average prevalence of other fluency disorders (when compared to the population at large). An in-depth analysis of the available data indicates that some of these genetic syndromes show patterns of stuttering that may be indicative of only that syndrome (or similar syndromes) that can be differentially diagnosed from developmental stuttering. Among these patterns are the word-final nonfluencies noted in Prader-Willi syndrome; the presence of stuttering in the absence of secondary behaviors noted in Prader-Willi syndrome and; the presence of palilalia, word-final and word-medial nonfluencies, and word-medial and word-final nonfluencies in Tourette syndrome. Implications for future research are discussed in light of these findings. Educational objectives: The reader will be able to: (1) describe the various different genetic syndromes that are associated with fluency disorders; (2) describe the types of nonfluencies that are associated with the major types of genetic syndromes that have fluency disorders; (3) describe the behaviors that may assist in differentially diagnosing different types of speech characteristics associated with various genetic syndromes. (Contains 1 table.)