Transthecal digital block is an effective anesthesia. The purpose of this study was to analyze the effect of different anesthetic concentrations on the anesthetic level of transthecal block. From July 2003 to August 2003, 17 patients with trigger finger received local anesthesia by transthecal digital block. The patients were randomized to receive either 1 mL 1% lidocaine and 0.5 mL betamethasone (7 mg/mL), or 1 mL 2% lidocaine and 0.5 mL betamethasone. Anesthetic intensity was checked over different aspects of digits. The 2% lidocaine group showed significantly better pain scores over the dorsal aspect of the digits (p = 0.002). The most effective anesthesia was in the volar aspect of the digits. Anesthesia was least effective in the dorsum of the digit at the lower anesthetic dose.