The concept of average number of ligands has been extended to the case in which the complex species are regarded as the entities which take part in further successive complexing equilibria. The mathematical relation between Bjerrum's concept of n ̃ and the newly defined "average number of ligands" referring to any arbitrary complex species, MAn, has been derived. A new method has been elaborated for the calculation of stability constants. A programme for this method is submitted in Algol 60 publication code. The application of the method is illustrated with reference to the Ni(II)-ammine, Ni(II)-valine and Ce-glycolate system.