The laser photolysis of gold Au-III salts embedded in micelle cores of block copolymer micelles derived from polystyrene-poly-4-vinylpyridine was studied. Two types of polystyrene-poly-4-vinylpyridines having different block length have been employed, producing micelles with different properties. The influence of the type of gold salt, loading rate, presence of water, micelle characteristics, and some other parameters on the rate of reduction and gold colloid formation were investigated. The presence of water in the system containing HAuCl4. 3H(2)O was found to accelerate the Au-III reduction, while the gold colloid size was not affected (about 3 nm). The substitution of HAuCl4. 3H(2)O with AuCl3 results in much slower accumulation of Au-I species with subsequent slower nucleation of gold colloids that results in bigger particles with mean diameter of 6.0 nm. Increasing the amount of metal compound was found to lead to an increase of the particle size.