The present dissertation investigates the binary aggregation of two anionic azotic dyestuffs induced by alkaline earth ions in aqueous solution. The main experimental techniques used are static and dynamic light scattering and small angle x-ray scattering. UV/vis spectroscopy, transmission electron microscopy and mass spectroscopy are applied as complementary methods.Priority is given to a time-dependent quantification of structural parameters of the aggregates and to the interpretation of the aggregation process by means of suitable kinetic models. Besides, the composition of the formed aggregates is further investigated and information on their branching behaviour and their tendency to form networks is obtained.The dyestuff aggregation is induced by combining an alkaline earth solution with a solution containing the two azo dyes. Immediately after the two solutions are mixed, a very short (< 1s) nucleation phase sets in. The nuclei formed here continuously grow to fibre-like dyestuff aggregates by gradually adding further dyestuff building units. The rate of aggregation strongly depends on the type and the concentration of alkaline earth ions. Within full-grown aggregates, the two azo dyes adopt a stoichiometric ratio of 1:1 and the negative charges of the dyestuff molecules balance the positive charges of the alkaline earth ions. The spatial distribution of the latter along the fibre-like aggregates is homogeneous.