The present study examines the relative contributions of the nasal septum and airway volumes to the total volume of the fetal nasal capsule. For comparative purposes, 29 human fetal specimens (20 "normal" and 9 with cleft lip and palate (CLP] were celloidin embedded, sectioned, and stained with hemotoxylin and eosin. The specimens ranged from 8 to 21 weeks in postmenstrual age. Photomicrographs of the serial sections allowed selected anatomic structures to be computer digitized, reconstructed as three-dimensional computer representations, and quantified. Various nasal capsule component measurements were compared with overall nasal capsule size values, producing relative size indices. Significant differences (p less than 0.05) were noted between the "normal" and CLP fetal samples in the relative sizes of the nasal capsule, airways, and septum. Relative mean CLP nasal capsule volume was 14% smaller than normal, relative mean CLP airway volume was approximately 43% smaller than that of the normal specimens, whereas relative mean CLP septum volume was approximately 45% larger. Aspect ratios (i.e., height:width ratios) were utilized for shape analysis of the nasal septal cartilage and indicated that the CLP septal shape was one of increased width relative to height compared with normal specimens. Results were consonant with clinical impressions of nasal capsule deficiency in the CLP nasal capsule and revealed some new structural associations in the fetal nasal capsule.