The use of cellular telephones has increased dramatically during the 1990's in 
the world. In the 1980's the analogue NMT system was used whereas the digital 
GSM system was introduced in early 1990's and is now the preferred system. Case 
reports of brain tumours in users initiated this case-control study on brain 
tumours and use of cellular telephones. Also other exposures were assessed. All 
cases, both males and females, with histopathologically verified brain tumour 
living in Uppsala-Orebro region (1994-96) and Stockholm region (1995-96) aged 
20-80 at the time of diagnosis and alive at start of the study were included, 
233 in total. Two controls to each case were selected from the Swedish 
Population Register matched for sex, age and study region. Exposure was assessed 
by questionnaires supplemented over the phone. The analyses were based on 
answers from 209 (90%) cases and 425 (91%) controls. Use of cellular telephone 
gave odds ratio (OR) = 0.98 with 95% confidence interval (CI) = 0. 69-1.41. For 
the digital GSM system OR = 0.97, CI = 0.61-1.56 and for the analogue NMT system 
OR = 0.94, CI = 0.62-1.44 were calculated. Dose-response analysis and using 
different tumour induction periods gave similar results. Non-significantly 
increased risk was found for tumour in the temporal or occipital lobe on the 
same side as a cellular phone had been used, right side OR = 2.45, CI = 
0.78-7.76, left side OR = 2.40, CI = 0.52-10.9 Increased risk was found only for 
use of the NMT system. For GSM use the observation time is still too short for 
definite conclusions. An increased risk for brain tumour in the anatomical area 
close to the use of a cellular telephone should be especially studied in the 
future.