BACKGROUND There is little published information about segmental hypo- and hyperpigmentation pigmentation disorder (SegPD) although it is a relatively common problem in paediatric dermatology. OBJECTIVES To define the spectrum of disease, clinical presentation and associations in cases of SegPD and to clarify further the terminology in defining patterned hypo- and hyperpigmentation in children. METHODS This was a retrospective review of cases in an academic paediatric dermatology practice. Thirty-nine patients referred for dermatological evaluation were diagnosed with SegPD. Demographic and clinical features, and distribution and frequency of extracutaneous abnormalities were measured. RESULTS Twenty female and 19 male patients were included in the study; 33 out of the 39 were referred specifically for a pigmentation abnormality. The mean age at onset was 3·4 months (median age 0·25 months). Family history was positive in two patients. Most (30/39; 77%) had segmental hyperpigmentation whereas nine of 39 (23%) had hypopigmentation. Patches were more often delineated at the ventral midline (32/39) than on the dorsal midline (7/39). The distribution of lesions was as follows: areas of the torso were most often affected (77%) and when the face, neck, arms and legs were affected pigmentation usually extended onto the torso; six patients had SegPD localized to the face. Only three of the 39 patients had extracutaneous abnormalities - atrial septal defect, strabismus with retinal hypopigmentation and a bronchogenic cyst - but the relationship to SegPD was uncertain and none had neurological abnormalities. CONCLUSIONS SegPD is a relatively common pigmentary anomaly and most affected individuals are otherwise healthy. We propose reviving the term 'segmental pigmentation disorder' coined by Metzker and colleagues to describe children with segmental and block-like hypo-/hyperpigmentation with midline demarcation.