This publication, written in Dutch, describes the effectiveness in terms of the rate of recidivism of five short-term job training courses offered since 1991 at the detention center Havenstraat in Amsterdam. A total of 56 juvenile detainees attended these courses during the last stage of their detention. The first three groups were trained to become skilled junior roustabouts, jacks-of-all-trades on a drilling platform. The last two groups attended a training course as industrial cleaners in the petrochemical industry. Passing the course was to result in a paid job. For each course, several employers guaranteed to hire a number of trainees. For a period of up to 30 months after their release, information was collected concerning the careers of the 56 participants. Additionally, the criminal records of the first three groups, involving 33 participants, were analyzed to establish recidivism rates. Overall the results are mixed. Results show, inter alia, that immediately after the training course, 50 percent of the participants held a job as a roustabout or industrial cleaner with one of the companies involved. A small number of participants chose another line of work. The others, 41 percent, were unemployed once they were released, partly because they dropped out as soon as the course ended, partly because for economic reasons some employers eventually failed to keep up their promise to hire qualified trainees. Long-term results show that 10 out of 33 participants had a steady job or worked regularly for most of the 18 months following their release. In terms of work and the recidivism rate of the particular group, as many participants were successful as there were who failed. The highest recidivism rate was experienced by the group of 14 participants who had been predominantly unemployed after release. It remains unclear how these results should be interpreted. The authors urge further study and a joint effort on an administrative level to increase local opportunities for the successful job placement of prisoners.