PURPOSE: The objective of this study was to assess if an increase in electrical impedance was associated with intraneural (sub-epineural) needle tip placement. METHODS: Two electrical impedance measurements were carried out in each of 140 peripheral nerve blocks. The first measurement was performed at a distance of 0.5-1 cm from the nerve trunk (reference value), and the second measurement was performed close to the nerve, either immediately before local anesthetic injection if no nerve puncture was suspected, or immediately before repositioning the needle if nerve puncture was suspected. Nerve puncture was suspected if any one of the following indications was present: pain or paresthesia; motor responses with a minimal stimulating current 4.3% increase in electrical impedance may indicate accidental nerve puncture during peripheral nerve block.