Olfactory detection thresholds for 11 structurally diverse musk odorants and one non-musk odorant were obtained from 32 subjects. Hierarchical cluster analysis produced four groups of subjects. One group (n = 12) was uniformly sensitive to all musks; another (n = 16) was uniformly insensitive. Two groups of subjects contained otherwise insensitive individuals who were exceptionally sensitive to cyclopentadecanone and musk xylol (n = 2) and to delta9-hexadecenolactone and tonalid (n = 2) respectively. We propose that the latter two groups are odor perception phenotypes (MSHM1 and MSHM2) that consist of multiple, specific hyperosmias to musk odorants. Chem. Senses 21: 411– 416, 1996.