The aim of the prospective study was to assess the exact kidney temperature and the effect of surface cooling of the kidney during the time of vascular anastomosis. Twenty-two renal graft recipients were incorporated into our study. We used an electronic temperature measurer provided with a needle-shaped probe pierced into the body of the kidney. The temperature was recorded every 5 min. The mean temperature of the kidney at the beginning of anastomosis (T0) was 8.87 +/- 3.97 degrees C and 17.95 +/- 5.1 degrees C at the end (Tend). The striking finding of this study was that the mean Tend delayed kidney function-negative in [ATN(-)] recipients was significantly lower than in the ATN(+) group; respectively, 14.86 +/- 3.6 degrees C and 19.71 +/- 5.07 degrees C. Therefore, we have divided all recipients according to Tend (< 15 degrees C and > 15 degrees C) in an attempt to assess the direct influence of kidney temperature on early graft function. In nine cases, a temperature below 15 degrees C was recorded and in 13 cases it exceeded 15 degrees C at the end of anastomosis. The mean cold ischemia time and anastomosis time were not different in these recipients. Delayed graft function occurred in 14 recipients; in 3 of 9 (33.3%) recipients from group Tend < 15 degrees C; and in 11 of 13 (85%) from group Tend > 15 degrees C. One case of primary non-function was observed (Tend > 15 degrees C). This study documents the value of effective cooling of the kidney during the time of vascular anastomosis. Since in most clinical reports the significance of the second warm ischemia was assessed only by the duration of the anastomosis, without measurement of the actual organ temperature, this may explain the different findings in our studies.