The sample consisted of 133 white, male adolescents ages 13-16, about 10 percent of the population of such youths in the city where the sample was drawn. The population was first stratified according to police-recorded delinquency and a socioeconomic breakdown of census tracts, and random subsamples were drawn. Interviews obtained data on self-reported delinquency. Although the validity of the I-level developmental continuum requires further testing, no difficulty was encountered in classifying all the sample. I-level was found to be related to age and IQ as expected, with age being the more strongly related. Socioeconomic status (SES) was unrelated to I-level. When relationships were investigated between the I-level subtypes and the demographic variables of age, SES, and IQ, it was found that the relationship between I-level and age was strongest among the youths who did not fit the I-level subtypes and very weak among those who did. This finding supports the contention that several of the I-level subtypes, especially those at I-level 3, represent ways in which personality development becomes blocked. Although I-level was found not to be related to either police-reported or self-reported delinquency measures for the total sample, for the older half, a much greater proportion of youths classified at I3 than at I4 had official records of delinquency. Thus, as the immaturity of the I3 level becomes less appropriate because of expectations related to age, coming to the attention of legal authorities becomes more likely. Tabular data and 46 references are provided.