Peutz-Jeghers' syndrome (PJS) is a disease with autosomal dominant inheritance, which is characterised by gastrointestinal hamartomata and characteristic melanin pigmentation. Three candidate sites for a PJS locus have recently been proposed, chromosomes 1p31-p32, 6q25 and 6p11-cen. At the first of these sites, a multipoint LOD score of 4.00 had been found, strongly suggesting genetic linkage to PJS. The last two candidate sites were suggested by the chromosomal breakpoints of a patient with an inv(6) and PJS. We have analysed up to 34 families in order to test each of the three candidate sites for linkage to PJS. No evidence was found in support of a Peutz-Jeghers' syndrome locus on chromosome 1p31-p32. The candidate region on 6q25 was also excluded. The region close to the centromere of chromosome 6 has not been excluded and there is some evidence of linkage to a marker near 6cen, although genetic heterogeneity in PJS must be proposed to account for a gene at this site.