There are reports that complex regional pain syndrome, type I (reflex sympathetic dystrophy; CRPS-I/RSD) can spread from the initial site of presentation, but there are no detailed descriptions of the pattern(s) of such spread. We describe a retrospective analysis of 27 CRPS-I/RSD patients who experienced a significant spread of pain. Three patterns of spread were identified. 'Contiguous spread (CS)' was noted in all 27 cases and was characterized by a gradual and significant enlargement of the area affected initially. 'Independent spread (IS)' was noted in 19 patients (70%) and was characterized by the appearance of CRPS-I in a location that was distant and non-contiguous with the initial site (e.g. CRPS-I/RSD appearing first in a foot, then in a hand). 'Mirror-image spread (MS)' was noted in four patients (15%) and was characterized by the appearance of symptoms on the opposite side in an area that closely matched in size and location the site of initial presentation. Only five patients (19%) suffered from CS alone; 70% also had IS, 11% also had MS, and one patient had all three kinds of spread. Our results suggest that CRPS-I/RSD spread may not be a unitary phenomenon. In some it may be due to a local spread of pathology (CS); in others it may be a consequence of a generalized susceptibility (IS). In the MS case, spread may be due to abnormal neural functioning spreading via commissural pathways. Alternatively, we discuss the possibility that all three kinds of spread may be due to aberrant CNS regulation of neurogenic inflammation.