Methods for genotyping polymorphisms using allele specific probes are disclosed. A training set is used to generate a model for each polymorphism to be interrogated. The training set is used to obtain an estimate of the asymmetry between an intensity measurement for a first allele and an intensity measurement for a second allele of the same polymorphism. The intensity measurement obtained for a test sample is adjusted using the estimate of asymmetry prior to using the intensity measurements to make a genotyping call. In preferred embodiments the adjustment is applied to polymorphisms that have a likelihood of being heterozygous that is above a specified threshold.