Because scanning probe microscopes produce three-dimensional data of almost any solid they have a strong potential as metrological tools. Results are presented from the first international intercomparison between four national metrology laboratories. On three-dimensional calibration standards the mean deviations between instruments were typically <2% in the x direction, <5% in the y direction, and <10% in the z direction. Eight samples were circulated for roughness measurements and 19 roughness parameters were calculated for each image. In the range where the scanning probe microscope measurements overlapped with classical techniques (profilometers) the agreement was good. Also a gauge block of hardened steel (approximate to 900 HV) with an array of Vickers indentations having diagonal lengths ranging from 3 to 60 mu m was circulated and measured.