Aim. The rock climbing (RC) is a recent sport practiced on artificial or natural rock faces. This study compared the efficiency, i.e., the ratio between energy cost and mechanical work, in two groups of rock climbers (experts=E and novices=N), with the purpose of relate this parameter with the athlete’s skill. Methods. Six experts and 4 novices male climbers (mean age 44.7±4.9 and 22,7±1,3 years respectively) were engaged for the study. In lab subject’s physiological profile and hand strength were evaluated. Maximal oxygen consumption (V.O2max), carbon dioxide production (V.CO2max), expiratory ventilation (V.Emax) and heart rate (HR) were assessed. Moreover, the maximal voluntary contraction (MVC) on a strain-gauge handgrip dynamometer was measured. During the climbing on a natural rock face a portable metabolimeter was used to measure V.O2, V.CO2max, HR and VE every 15 seconds. Blood lactate was measured with a portable lactacydimeter during recovery. Results. In lab measurements, no significant differences were found in aerobic and strength profile between E and N. On rock face, E performed better than N, showing a shorter time of ascent (219±25 vs 375±170 s), lower cost of exercise (1851±690 vs 3859±1363 J kg-1) and less lactic debt (26±22 vs 211±80 J kg-1). The efficiency of E resulted as almost twice that of N, being 17.2±4.64 vs 6.9±2.18 J.100/J respectively. Conclusion. Present results suggest that efficiency is the best parameter to evaluate of technical proficiency in RC athletes.