The report gives an account of comparisons of the optical frequencies of I2-stabilised He-Ne lasers at 473 THz (633 nm) performed at Bureau International des Poids et Mesures (BIPM), Sèvres, France during week 24, June 12-16, 1989. The lasers, SP1 and BIPM2 belong, respectively, to Statens Provningsanstalt, Borås, Sweden and BIPM. Systematic investigations were made of the dependence of the optical frequency of laser SP1 on a number of parameters such as intracavity power, modulation width, integrator and lock-in amplifier voltage offsets, iodine cell and cavity misalignment. It was found that the laser SP1 differed in optical frequency from the laser BIPM2 by +8.0 kHz, at a one-way intracavity power of 23.7 mW. The standard deviation in the frequency difference measurement was 1.6 kHz, whereas the reproducibility of the laser SP1 frequency was estimated to be ±20 kHz.