BIPM activities related to realization of the definition of the metre

The results are presented of frequency comparisons of laser radiations at /spl lambda//spl ap/3.39 /spl mu/m, /spl lambda//spl ap/633 nm, and /spl lambda//spl ap/515 nm used for the realization of the metre. Work on lasers at /spl lambda/=532 nm, recently recommended by the CIPM, and on iodine-stabilized extended-cavity diode laser at 633 nm are described. Activities in gravimetry and in nanometrology are also presented.