The Panel on Plant Health performed a pest categorisation of Spiroplasma citri, the causal agent of citrus stubborn disease, horseradish brittle root and carrot purple leaf. S. citri is a well-defined species of the genus Spiroplasma, a group of helical wall-less bacteria (Mollicutes) mainly associated with arthropods. Routine molecular detection methods are available and are appropriate for identification. S. citri is not known to occur in most of the EU Member States. Among citrus-growing countries, only Croatia, Greece, Malta and Portugal do not report S.citri. The disease seems to be widespread only in Cyprus. S. citri is included in Annex II, Part A, Section II of Directive 2000/29/EC. The insect vectors Circulifer haematoceps and C. tenellus are included in the same Directive, Annex II, Part A, Section II. Citrus, the main host plant (as a symptomatic host crop), is listed (a) in Annex III, Part A, (b) in Annex IV, Part A, Section II, (c) in the same annex, Part B, and (d) in Annex V, Parts A and B, Section I. S. citri is disseminated by plants for planting and by seven species of leafhoppers (Cicadellidae), of which only three species, C. tenellus, C. haematoceps and C.opacipennis, are reported in the EU. Besides the rutaceous hosts, more than 33 other plant species from 12 different families can be hosts, even if only some may show symptoms. Ecological conditions in the risk assessment area are suitable for the establishment and spread of S. citri, at least where citrus is currently grown. Yield reductions on citrus crops are reported from Cyprus, with reduction in fruit size, weight and quality. Infected planting material could contribute to the dissemination of S. citri, as well as the insect vectors. In areas with a hot, dry climate, the impact on the yield and quality may be high.