EDITOR—Hand held cellular telephones, using pulse modulated signals of frequency 870-995 MHz, are being used increasingly. Most reports of health symptoms related to use of these phones are anecdotal. We undertook a cross sectional study of a community in Singapore to study the prevalence of specific central nervous system symptoms among users of hand held cellular phones compared with non-users and to determine any association of risk factors and central nervous system symptoms among users of the phones.1

From a sampling frame of all flats in a large town we conducted a one stage random cluster sampling of 808 individuals, who were interviewed by trained medical students …