Rigid nasendoscopy is a commonly used method of examining the nasal cavity and postnasal space. Co-phenylcaine is useful for its vasoconstrictive and anaesthetic properties, but the length of time allowed for it to take effect is variable. We performed a single-blind, randomized, controlled trial to determine whether it was better to allow one or 10 minutes for co-phenylcaine to take effect. Fifty patients were randomized into two groups, 25 in each. Patients in the 10 minute group experienced less discomfort (p=0.02) and less pain (p=0.018) than those in the one minute group. Ease of examination was also greater in the 10 minute group, as was the quality of the image obtained (p<0.001).