A near-field/far-field transformation procedure is described which is based on cylindrical mode expansion techniques and provides the capability for dealing with probes of any directivity. The principle of the method is demonstrated by computer simulation and the approach is validated in practice by predicting the 2-dimensional far-field patterns of slotted waveguide arrays. The near-field data is acquired with directive probes of up to 9 wavelengths in size at ranges of 0.1 D2/λ The effects of probe position errors are also discussed.