A factorial design is applied to the optimization of the determination of dimethyltin chloride by hydride generation gas phase molecular absorption spectrometry (HG-GPMAS). A method is described for the determination of dimethyltin chloride after conversion into gaseous dimethyltin hydride by adding a sodium tetrahydroborate (III) solution. The hydride generated is collected in a liquid nitrogen cryogenic trap. This is revolatilized, driven to the quartz flow cell and measured with gas phase molecular absorption spectrometry (GPMAS) with diode array detection. A Plackett-Burmann design is used for the study of the factors that influence the absorption signal. The optimization of these factors is performed using a central composite design. The spectra obtained over a wide range of wavelengths, 190-220 nm, allow the multivariate calibration to be studied. The parameters affecting the production and collection of the dimethyltin hydride are studied. The detection limit obtained is 3.2 ng ml(-1). The precision (RSD=4.1%) is calculated from a solution containing ten times the corresponding detection limit. The recoveries (99-108%) are satisfactory. A study is made of the influence of several interferent ions (hydride generators, transition metals and anions) in the presence of dimethyltin chloride.