Lack of assertiveness is considered, in the sense of the theoretical concept of Ullrich de Muynck and Ullrich, to be due to such components as 1. abnormal attitude toward oneself, 2. fear of criticism and failure, and 3. inadequately developed social skills; after this, the term 'assertiveness' is defined. Previous therapeutical approaches to the remedying of unassertiveness and the underlying theoretical assumptions are critically examined and discussed with particular reference to their effectiveness. These include the training programs developed by Salter and Wolpe which are characterized by certain onesidedness as well as the concept of Ullrich de Muynck and Ullrich, which has a sound theoretical basis and a rather differentiated or specialized structure. Reference is also made to the author's own research projects.