Since 1961, the Community Treatment Project (CTP) has handled seriously delinquent male and female offenders who have been committed from juvenile courts to the state correctional system from four California communities. Rather than being institution alized for several months, these youths, ages 13 to 19 at intake, are placed directly into a small caseload, intensive, community- located parole program: CTP. There, after being "matched" with a parole agent, they receive "differential" or relatively individual ized, as well as long-term, treatment. An "interpersonal maturity level" system is used to classify youths and as one important basis for establishing treatment objectives and techniques.Comparative effectiveness of the experimental (CTP) and control (traditional) programs was evaluated in terms of six separable out come measures: suspensions, recidivism, discharge, psychological tests, etc. E-C comparisons indicate that the E program has been able to handle a large majority of eligible youths (89 percent) at least as effectively as has the traditional program, while ten percent do better within the traditional program. Close to 25 percent do rather poorly within both types of program. A major objective of CTP—Phase Three (1969-1974) is that of developing more effective techniques and settings for working with this latter, rather sizable, "unsuccessful" group. Another objective is that of determining whether the CTP approach can be applied successfully to a wider range of offenders than have been handled to date — e.g., those committed from adult courts and/or for seriously assaultive offenses. Five main factors are mentioned as having made a sub stantial contribution to the comparative effectiveness of CTP during 1961-1969.