a b s t r a c tWe give a construction of k-regular graphs of girth g using only geometrical and combinatorial properties that appear in any (k; g + 1)-cage, a minimal k-regular graph of girth g + 1. In this construction, g ≥ 5 and k ≥ 3 are odd integers, in particular when k − 1 is a power of 2 and (g + 1) ∈ {6, 8, 12} we use the structure of generalized polygons. With this construction we obtain upper bounds for the (k; g)-cages. Some of these graphs have the smallest number of vertices known so far among the regular graphs with girth g = 5, 7, 11.