Barth syndrome is an X-linked disorder characterised by cardioskeletal myopathy of variable severity usually fatal in childhood, and neutropenia. We ascertained a large pedigree with affected males in 3 generations. All affected males had dilated cardiomyopathy, with endocardial fibroelastosis (EFE) in some. The locus for Barth syndrome in this family was found to be closely linked to DXS52 (z = 2.78, θ = 0.0). The family was nonrecombinant for DXS52 in distal Xq28, but recombinant for DXS374 which maps proximal to DXS52. This localised Barth syndrome distal to DXS374, confirming a previous localisation to distal Xq28. As yet there is no evidence for genetic heterogeneity of Barth syndrome.