An abnormal short-lived female infant with almost complete trisomy 13 (pter leads to q32 or 33) and partial monosomy 15 (pter leads to q14 or 15) resulting from an adjacent 2 meiotic disjunction of a paternal reciprocal translocation is described. Cases with monosomy of chromosome 15 material are reviewed. It appears likely that monosomy of an interstitial long arm segment, approximating to 15q21 leads to 24, imparts the lethality associated with the full monosomic condition. Adjacent 2 disjunction in man has been further characterised by reviewing the literature.