This study compared the posterior and popliteal fossa approaches for sciatic nerve block. Patients scheduled to undergo foot surgery were allocated randomly into one of two groups: group A (n = 20) received sciatic nerve block via the posterior approach and group B (n = 20) received a block using the popliteal fossa approach. All blocks were performed with the aid of a peripheral nerve stimulator and alkalinised 0.5% bupivacaine with 1 in 200,000 adrenaline was injected in a dose of 2 mg.kg-1. Nineteen of 20 blocks in group A were successful compared with nine of 20 in group B (p less than 0.01). There was no significant difference between the groups in respect of time to onset or duration of block. Patients in group B reported less discomfort during performance of the sciatic nerve block but required supplementary nerve blocks more frequently. We recommend the use of the posterior approach for sciatic nerve block.