The objective of this randomized, double-blind, placebo-controlled clinical trial was to determine whether a topical anesthetic agent (tetracaine) provides effective local analgesia prior to radial arterial puncture. Tetracaine or placebo gel was applied 45 min prior to arterial puncture to patients who were referred for elective arterial blood gas. The primary outcome was the patient's perception of pain associated with the procedure as measured by a visual analog scale. Fifty patients were randomized into the study, 24 received tetracaine and 26 placebo. Mean pain score on the visual analog scale was 26.2 +/- 32.6 for the tetracaine-treated patients and 23.8 +/- 27.4 for the placebo-treated patients (P = 0.78). Mean time from the first skin puncture to successful procurement of 1 ml of arterial blood was 70 +/- 103s in the tetracaine group and 49 +/- 48s in the placebo group (P = 0.40). Difficulty of arterial puncture as assessed by the respiratory therapist performing the test was identical for the two groups (P = 0.86). We conclude that tetracaine gel did not decrease patient's perception of pain associated with arterial puncture, nor did its use facilitate the ABG procedure.