The frequency and significance of a selected type of movement mannerism, nailbiting, have been studied by the interrogation and observation procedures in a sampling of 2297 white and 150 Negro recruits.(1) Nail-biting, regardless of its frequency and severity, was present in 23.2 per cent. No difference in prevalence was found between volunteers and naval draftees. No significant difference in frequency was apparent between the white and Negro samplings.(2) Statistical measures of central tendency are held to be inadequate means for the determination of the significance of this movement mannerism. The meaning of this and other related patterns of response must always remain the problem of the individual case.(3) For the military psychiatrist it is maintained that the tendency to look upon nail-biting always as an index of psychoneurotic or other psychopathological states is not supported by the facts. The nail-biting mannerism is of value in the military screening examination only if properly interpreted.(4) The important point is the manner in which the recruit reacts to the evidence. If he denies, evades, rationalizes, or expresses in other ways his general instability, the psychiatrist obtains important guides for further investigation. The high frequency is noted with which men, responding in these manners, were held over on other counts for additional neuropsychiatric study.(5) While it is undoubtedly true that nail-biting is always significant within the personality pattern of the individual, this mannerism is far from always an index of abnormality sufficient to disqualify a recruit for basic military training.(6) Nail-biting in adult males may, from one point of view, illustrate the "strangle hold" that childhood habits may come to possess.(7) In the sampling of 2297 recruits roughly one man in every four was a nail-biter. Of the 192 detained for further observation roughly one man in every four exhibited this mannerism.