Cardiorespiratory responses during arm-stroke-only swimming with and without the aid of paddle were compared in seven trained swimmers. Water flow rate was started at 0.80 m.s-1 and was increased by 0.05 m.s-1 every 2 min up. to 1.00 m.s-1. Subsequently, the flow rate was increased by 0.05 m.s-1 every minute until exhaustion. At given submaximal water flow rates, oxygen uptake, heart rate (fc), pulmonary ventilation (VE) and respiratory frequency (fR) during swimming using hands alone (H) were significantly higher than when aided by paddles (P). There were no significant differences in tidal volume (VT) between H and P. The subjects were able to swim significantly faster using paddles (P < 0.05); however, no significant differences between H and P were found in peak oxygen uptake (VO2peak, Fc, VE, FR, VT and the blood lactate concentration at which VO2peak was obtained (P > 0.05). These results would suggest that the ability to swim faster with paddles does not depend on higher energy production but may be attributed to higher propelling efficiency.