We observed three siblings with ectromelia of the upper extremities and the HoltOram syndrome. Manifestations of this syndrome were present in nine persons in four generations of the family. Partial deletion of the long arm of a B group chromosome was found in two siblings. The abnormal length of the B group chromosomes in one child and the father could be estimated only after measurements. These changes may be derived from a different degree of spiralization of the paired chromosomes, but they may be caused by a loss of chromatin. The osseous anomalies in our patients are probably related to the chromosomal structural changes.