The change in the pulse repetition frequencyc/2Lof a He&sngbnd;Ne laser, mode‐locked by a neon absorption cell, has been found to vary approximately asI−1/3, whereIis the average power output of the laser. Asc/2Lis changing, the pulse width also changes approximately asI−1/3. The corresponding round trip transit times 2L/care compared to an estimate of the empty cavity transit time obtained by an extrapolation of the data and also a direct measurement. The He&sngbnd;Ne and Ne media introduce an additional positive delay of 4–6 psec to the cavity transit time of 10 nsec; this delay is comparable to that estimated from group velocity considerations.