Leaves of 13 interspecific and intergeneric citrus somatic allotetraploid hybrids were analysed and compared with those of their respective parents (lime, lemons, citron, orange, kumquat, poncirus and mandarin) with regards to their sesquiterpenoid contents (µg/g dry weight). The hybrids do not fully retain their parental traits. sesquiterpenoid production is much reduced (by -65-90%) in hybrids compared with the sum of their parents. The peculiar behaviours of some compounds were described. Statistical analyses were conducted on a qualitative (the presence/absence of each compound in parents and hybrids) and quantitative (the recovery of each compound in hybrids expressed as a percentage of the sum of its concentration in their parents) basis. Mandarin exerts a strong dominance over its derived hybrids by greatly lowering the production of most compounds, while the expression of parental genomes was more balanced in hybrids having grapefruit or sweet orange as a parent. This decrease in the ability to synthesize sesquiterpenoids could be due to both the tetraploid nature of the hybrids and the dominance of one or other parental genome.