INTRODUCTION: The ultrasound-guided transversus abdominis plane (TAP) block is used to treat postoperative pain after abdominal surgery. Abdominal wall sensory nerves are anaesthetised by injecting local anaesthetics into the neurofascial plane between the internal oblique and the transversus abdominis muscles. Sensory assessment of a TAP block may guide the decision on the extent of the block. The purpose of this study was to investigate if the dermatomal extent of sensory blockade after injection of 20 ml 0.5% ropivacaine bilaterally into the TAP can be assessed using cold and pinprick sensation. MATERIAL AND METHODS: Subcostal TAP block was performed bilaterally in 20 awake patients scheduled for elective abdominal surgery. Sensory change in dermatomes T4-L4 was tested with pinprick using a blunt needle and cold disinfectant swabs after 10, 20 and 30 minutes. RESULTS: Data from 20 patients (40 blocks) were analysed. Eighteen patients registered sensory change after subcostal TAP block, and dermatomes T10-T12 were blocked after 30 minutes in all of these patients. Spread of sensory change to dermatomes T5-L3 was variable. CONCLUSION: This study confirmed that the dermatomal extent of a sensory blockade after a single-shot subcostal TAP block can be assessed using cold and pinprick sensation. FUNDING: not relevant. TRIAL REGISTRATION: The study was registered at clinicaltrials.gov with the registration number NCT01024868.