We at MIKES have developed an optical frequency comb for metrological applications. Ultra-short pulses on the femtosecond scale coming from a mode-locked Ti:S laser are focussed to a microstuctured fibre. Due to nonlinear interactions in the fibre, a frequency comb covering the wavelength range 500–1100 nm is generated. When the comb is phase-locked to an atomic clock, the optical frequencies of all the comb components are known with the accuracy of the primary frequency standard. Hence, the comb can be used to determine an unknown laser frequency by measuring the frequency difference between the unknown laser and the nearest comb component.