Feeds import - Skip importing item based on some condition
You can do this using hook_feeds_presave to check the data prior to it being saved.

function mymodule_feeds_presave(FeedsSource $source, $entity, $item) {

  // check that this is fired only for the importer being used
  if($source-&gt;importer-&gt;id=='my_user_importer'){

    // check that the age is over 18
    if($item['age'] &lt; '18'){
      $entity-&gt;feeds_item-&gt;skip = TRUE;
      drupal_set_message(t("Skipping user who's age is below 18", 'warning');
    }
  }
}