An assessment was made of the possible significance of hypocotyl length in the identification of brussels-sprout varieties. The investigation was based on the analysis of 162 samples of varieties currently in commerce, a search for sibs amongst supposed F1 varieties and the comparison of known and unknown varieties. Varieties were found to vary consistently from one another, although environmental and environmental by genotype interaction effects were significant. It was found that sibs could be recognized easily in F1 hybrid samples known to contain them and it was inferred, and later evidence confirmed, that they were present in other F1 hybrids. Up to 8 out of 13 F1 varieties were correctly identified from coded samples and it was concluded that hypocotyl characteristics could be used with other measurements in the description of new introductions.