The vertical tabs don't show when is one vocabulary I am working in Drupal 6, and I am using the Hierarchical select. If my taxonomy consists in two or more vocabularies associated to a content type, the vocabulary shows into vertical tabs but if my taxonomy consists in one vocabulary associated to a content type, the vocabulary doesn't show into vertical tabs.

I thank to you for your help.
It's the setting for "Minimum number of tabified fieldsets to show vertical tabs:" found at: /admin/settings/vertical-tabs

It's defaulted to 3, which means you must have 3 vocabs on the node type for it to put them in a tab... you can change the minimum value.