The incidence rate of childhood leukaemia varies internationally (about 4–40/10⁶ per year) with the lowest rates being recorded in black African children.¹ The data from population based studies on the incidence of childhood leukaemia in South Asia, including Pakistan, are lacking. The development of leukaemia has been considered as an infectious process.² However, the epidemiological evidence for the existence of childhood leukaemia virus has been regarded as naive. Also, the question whether childhood leukaemias have a tendency to occur in cluster remains un-answered.³ We conducted this study to determine if clustering of cases of childhood leukaemia at diagnosis in time and time and space if observed was more common than could be expected.

METHODS

Data collection was carried out between March 2002 and November 2002. All children diagnosed between 1 January 1995 and 30 May 2002 as having any form of leukaemia before their 15th birthday and were born and resident of Karachi, were included in the …