An automatic ultraviolet spectrophotometric method is described for the determination of ammelide, ammeline and melamine in the thermal decomposition products of urea; prior separation of the components is unnecessary. A Unicam SP3000 spectrophotometer is used to make absorbance measurements at several different wavelengths and at two pH values. From the absorbance values obtained the concentrations of the amino-s-triazines are calculated by using a computer to solve the appropriate simultaneous equations. The constants required in these equations are obtained by calibration of the spectrophotometer with solutions of the pure compounds. A semi-quantitative estimation of triuret is also possible. Interferences caused by biuret and cyanuric acid can normally be ignored, but corrections are required if large amounts are present.