A multivariate calibration procedure based on singular value decomposition (SVD) and the Ho-Kashyap algorithm is used for the tensammetric determination of the cationic detergents Hyamine 1622, benzalkonium chloride (BACl), N-cetyl-N,N,N-trimethylammonium bromide (CTABr) and mixtures of CTABr and BACl. The sensitivity and accuracy depend strongly on the nature of the detergent. Acceptable accuracy is obtained with a two-step calculation procedure in which calibration constants for the total concentration range of interest are used to guide the choice of a more specific set of calibration constants which are valid for a much smaller concentration span. For Hyamine 1622, concentrations in the range 5 × 10−6−2 × 10−4 M could be determined with an accuracy of ± 10−6 M. For CTABr, these numbers were 3 × 10−6−2 × 10−4 M and ± 5 × 10−7 M; for BACl, they were 2 × 10−3−9 × 10−2 g l−1 and ± 1 × 10−3 g l−1. In the mixtures of CTABr and BACl, the accuracies were ± 3 × 10−6 M and × 1 × 10−3 g l−1, respectively.