A method has been developed to measure the single‐pass gain of superradiant high‐gain pulsed lasers by comparing the intensities of single‐pass and double‐pass radiation. This method is used on the 7229 Å transition in Pb I and gives a maximum single‐pass gain of 63 dB in a 10 cm effective length of lead vapor. The gain is confirmed by line‐narrowing measurements and by power output measurements that are related to the theoretical intensities.