Variation in adult and seedling morphology within Eucalyptus series Subulatae subseries Spirales, a group of mallee and woodland tree taxa distributed across southern Australia, was examined. A total of 35 adult morphological characters and 13 seedling characters was included in the phenetic analyses of 150 individuals representing 40 populations covering all the taxa and the broad geographical distribution of the subseries and also including E. brockwayi and E. salmonophloia for comparative purposes. Based on phenetic analyses of adult and seedling characters, six taxa are recognised within E. subser. Spirales and seedling characters are important in delimiting these taxa. Of the seven subspecies of E. oleosa described by Johnson and Hill (1999), two subspecies, E. oleosa subsp. oleosa and subsp. repleta could not be distinguished from one another based on either adult or seedling morphology. Similarly, the three subspecies, E. oleosa subsp. ampliata, wylieana and victima, could not be distinguished. A new taxonomy for E. subser. Spirales based on phenetic analyses combined with extensive field, glasshouse and herbarium examination of all taxa in the subseries is presented. Six terminal taxa in the subseries are recognised, viz. E. delicata, E. longicornis and E. oleosa with subspp. oleosa, ampliata, corvina and cylindroidea. Within E. oleosa, E.oleosa subsp. oleosa and subsp. ampliata are not readily distinguishable on the basis of adult morphology alone. Eucalyptus oleosa subsp. repleta is synonymised with subsp. oleosa, and E. oleosa subspp. wylieana and victima with subsp. ampliata. Keys to the taxa of the subseries are presented.