The effect of intense training on endothelial proliferation, capillary growth and distribution of VEGF and bFGF was examined in human skeletal muscle. Two intermittent knee extensor training protocols (at ~150% [Study 1] vs. ~90% [Study 2] of leg VO2-max) were conducted. Muscle biopsies were obtained throughout the training periods for immunohistochemical assessment of capillarisation, cell proliferation (Ki-67 positive cells), VEGF and bFGF. In Study 1 microdialysis samples were collected from the trained and untrained leg at rest and during exercise and added to endothelial cells to measure the proliferative effect. After four weeks of training there was a higher (P<0.05) capillary to fibre ratio (Study 1: 2.4 ± 0.1 vs. 1.7 ± 0.1) and number of Ki-67 positive cells (Study 1: 0.18 ± 0.05 vs. 0.00 ± 0.01) than before training. Neither the location of proliferating endothelial cells nor capillarisation was related to muscle fibre type. The endothelial cell proliferative effect of the muscle microdialysate increased from rest to exercise both in the untrained (from 262 ± 60 to 573± 87 % of control perfusate) and the trained (from 303 ± 75 to 415± 108 % of perfusate) leg. VEGF and bFGF were localised in skeletal muscle- and endothelial cells and training induced no changes in distribution. The results demonstrate that intense intermittent endurance training induces capillary growth and a transient proliferation of endothelial cells within four weeks, with a similar growth occurring around type I versus type II muscle fibres.