The colour reactions of molybdoyttric acid and basic dyes (BD) in aqueous solution in the presence of poly(vinyl alcohol) were investigated. Three highly sensitive spectrophotometric methods for the determination of yttrium have been developed, based on the ion-assocation complexes of molybdoyttric acid with three basic dyes (BD), e.g. rhodamine B (RB), butyl rhodamine B (BRB) and nile blue (NB) in aqueous acidic solution in the presence of poly(vinyl alcohol) (PVA). Their spectrophotometric behaviors, such as the suitable conditions for the reactions, the composition of the ion-association complexes, and the effects of foreign ions, have been studied. The absorption maxima waves were at 590, 580 and 590 nm with apparent molar absorptivities of 3.53 × 105, 4.74 × 105and 4.99 × 105L mol−1cm−1, respectively. Beer's law was obeyed up to 3.5, 3.0 and 3.5 μg yttrium per 25 ml, respectively. The detection limits (3 [sgrave] blank) were 1.8, 2.6 and 4.8 ng ml−1, respectively, and for a 0.08 μg ml−1solution of yttrium the relative standard deviations were 3.2, 2.8 and 1.1%, respectively (n = 6). The proposed methods have been applied to the spectrophotometric determination of trace amounts of yttrium in magnesium alloys and some geological samples.