 This initiated an investigation carried out in 1983 at the Madrid Goethe-Institute, in which tandem pairs, a tandem course and teacher-steered phases were connected with each other and the linguistic progress was compared to a control group, who were also preparing for the 'Zertifikat DaF'.Results showed that the Tandem participants got better results in listening comprehension and speaking skills while they were less successful in reading and writing, even if their performance in the certificate as a whole was just as good as the control group.Another advantage was mutual mistake correction, which was fostered by increased language intake.