Due to demographic change it becomes more and more important to find a legally certain way to retain employees after they have reached the standard retirement age (so-called old-age pensioners). First, the question whether retirement ages in employment contracts, collective and works agreements are still admissible according to German and European law is critically analysed. What follows is one of the main emphases of the work: A study of the different possibilities to employ pensioners under employment law and the advantages and disadvantages for both parties to the employment contract (e. g. freelancer, agency model, hiring out of employees and mainly the restriction of employment contracts according to 41 s. 3 SGB VI and 14 TzBfG). There are also many questions concerning the dismissal of a pensioner. Finally, the question whether the current system of supplementary income limits under social security law remains appropriate is discussed and a proposal for reform is presented.