The aim of this study is to assess the effect of patient positioning and obesity on the height of block achieved during routine labor epidural analgesia. Forty patients weighing <80 kg were allocated to a control group and a further 40 weighing >100 kg to a study group. Half the patients in each group received an epidural injection in the lateral position, the remainder were in the sitting position. After insertion of an epidural catheter and injection of 12 ml of 0.25% bupivacaine plain the patients remained in position for a further 5 min. The height of block achieved, as assessed by loss of cold sensation, showed no difference between any of the groups. The results indicate that, for routine labor epidural analgesia, using 12 ml of 0.25% plain bupivacaine, neither patient positioning nor obesity affects the height of block achieved.