This volume contains most of the invited lecture series presented at the Nordic Summer School in Mathematics held at the University of Joensuu, June 1-12, 1981. The Summer School was devoted to the value distribution theory, the main emphasis being in several variables. The invited speakers were, in alphabetical order, W. K. Hayman, 0. Lento, S. Rickman, B. Shiftman and W. Stoll. The lecture series given by 0. Lehto has been published elsewhere; therefore it is replaced here by an introduction to Nevanlinna theory by S. Toppila.