The duration of tourniquet ischaemia was recorded in 1000 consecutive operations on extremities under a bloodless field, the average ischaemia time was 74.11 +/- 29.52 minutes. The duration of tourniquet ischaemia in meniscectomies was 58.47 +/- 15.91 minutes, in osteosynthesis of malleolar fractures 88.46 +/- 23.33 minutes and in operations for endoprosthetic replacement of the knee joint 131.19 +/- 11.24 minutes. In 85 cases the commonly accepted two hour limit for tourniquet time was exceeded without clinical complications. LDH and CPK levels in venous blood were studied in 15 operations. No significant changes were seen in LDH levels when recorded up to 24 hours following release of the tourniquet. CPK levels increased significantly (p less than 0.05) and highly significantly (p less than 0.005) when measured three hours and 24 hours after the release of the tourniquet, respectively. The results of the study suggest that two hours of ischaemia of the extremities is relatively well tolerated.