=== modified file 'modules/taxonomy/taxonomy.admin.inc'
--- modules/taxonomy/taxonomy.admin.inc	2010-03-07 23:14:20 +0000
+++ modules/taxonomy/taxonomy.admin.inc	2010-03-11 14:45:00 +0000
@@ -924,6 +924,7 @@
  */
 function taxonomy_vocabulary_confirm_delete_submit($form, &$form_state) {
   $status = taxonomy_vocabulary_delete($form_state['values']['vid']);
+  field_delete_field('taxonomy_' . $form['#vocabulary']['machine_name']);
   drupal_set_message(t('Deleted vocabulary %name.', array('%name' => $form_state['values']['name'])));
   watchdog('taxonomy', 'Deleted vocabulary %name.', array('%name' => $form_state['values']['name']), WATCHDOG_NOTICE);
   $form_state['redirect'] = 'admin/structure/taxonomy';