The variation shown by 60 characters (morphological, anatomical, embryological, chemical and cytological) is tabulated for the whole of the Ericaceae. The reliability of the characters and the observations on them are discussed, and it is emphasized that many characters are difficult to use because they are rarely restricted to one taxon. Six subfamilies are recognized. Within the Rhododendroideae seven tribes are recognized, the monogeneric Daboecieae being new; Epigaea is transferred to the Rhododendroideae from the Andromedeae and Diplarche from the Diapensiaceae. Calluna is placed in a new monotypic tribe within the Ericoideae. The extended Vaccinioideae includes the Arbutoideae; five tribes are recognized, of which the Enkiantheae and Cassiopeae are new. The Pyroloideae and Monotropoideae are left unchanged: a new subfamily, the Wittsteinioideae, includes the deviant monotypic genus Wittsteinia. A key to subfamilies, and to genera of the Pyroloideae, Rhododendroideae and superior-ovaried Vaccinioideae is given.