We present two techniques, of general use in radio astronomical interferometry, for analysing aperture synthesis data without employing phase information. In the first, a trial map is derived from observed amplitudes alone, and in the second, the true distribution of brightness is deduced from the trial map by an iterative procedure. These techniques are similar to those used in solving molecular structures from X-ray diffraction patterns. A practical test, using data from the 5C 7 survey, is presented.