Exocortis in citrus—an increasing problem for California growers—has emphasized the need for a rapid-indexing method for periodic testing of trees used as sources of budwood. Detection of this disease in symptomless citrus trees by field-indexing on sensitive indicator rootstocks has previously required from one and one half to more than five years. The practical method of indexing exocortis in glasshouse plants reported here caused symptoms to develop within one to five months.