A whole-genome scan was conducted to search for quantitative trait loci (QTL)affecting health traits in Finnish Ayrshire dairy cattle. The mapping populationconsisted of 12 bulls and their 491 sons in a granddaughter design. A total of150 markers were typed covering all 29 autosomes. The traits under study weresomatic cell score, mastitis, and a group of other veterinary treatments.Effects of the QTL and positions were estimated with the regression method. Whencarrying out interval mapping on each chromosome, cofactors were used to adjustfor QTL identified at other chromosomes. Empirical P-values were obtained bypermutation. Altogether 17 QTL were detected with genomewise significantP-values in the across family analysis. Quantitative trait loci affecting SCSwere identified on chromosomes 1, 3, 11, 18, 21, 24, 27, 29, and QTL formastitis on chromosomes 14, 18. Quantitative trait loci for other veterinarytreatments were found on chromosomes 1, 2, 5, 8, 15, 22, and 23. The allelesubstitution effects were from 0.5 to 1.7 genetic standard deviations. Thepositions of these health QTL did not overlap with milk QTL detected in previousstudies of the same population.