Hirschi and Gottfredson contend that the familiar inverted J-curve association between age and crime is invariant, inexplicable with social science variables, and involves no interaction between age and any variable that explains or correlates with crime. This paper first reviews the existing evidence pertinent to these three hypotheses. This is followed by a report on the research conducted by the authors to test the three hypotheses. The study focused on the inexplicability and non-interaction contentions by using variables from Gottfredson and Hirschi's own general theory of crime. Data were obtained from the Thirteenth Annual Oklahoma City Survey. In the spring of 1991, the Sociology Department of the University of Oklahoma interviewed a simple random sample of 394 adults aged 18 or older listed in the R.L. Polk Directory. Trained personnel later conducted face-to-face interviews, but respondents reported their crimes on separate answer sheets unseen by the interviewers. The examination of the three hypotheses yielded mixed results. The invariance hypothesis, i.e., that the relationship between age and crime is of an inverted-J form for all types of crime, proved problematic, because tax cheating, a white-collar crime, is visually related to age in a curvilinear manner, with the highest level during the middle ages; however, patterns for four of the five crime measures basically conform to the curve suggested by the invariance hypothesis. The test of the inexplicability hypothesis; i.e., that the relationship between age and crime cannot be explained with social variables, also produced mixed results; even though better measures might have produced more success, the results verify how difficult it is to account for age-crime associations. Finally, the tests of the non-interaction hypotheses, i.e., that the correlates and causes of crime do not interact with age, also yielded ambiguous results; one approach showed more interaction than would have occurred by chance alone, but another did not; however, most of the causes and correlates of crime in the data did not interact with age. 3 tables and 62 notes