This is a retrospective study of atrial screw-in leads implanted at the Singapore General Hospital from January 1988 to August 1990. There were 21 (13 female and 8 male) consecutive patients, with age ranging from 17 to 79 years (mean 55 years). Thirteen patients had sick sinus syndrome and the remaining eight patients had high grade AV block. Eleven patients had AAI, six had DDD and four had DDDR pacing modes respectively. Three different models of unipolar screw-in leads were used. Eight patients had Medtronic Model 6957, seven had Medtronic Model 4057 and six had Siemens-Pacesetter Model 1007 pacing leads implanted. At the time of implant, the measured P wave amplitudes ranged from 1 to 4.8 mV (2.5 +/- 1.1 mV) and the pacing thresholds ranged from 0.5 to 2.3 volts (1.21 +/- 0.51 volts). There were no acute complications at the time of implant. On follow-up ranging from one month to two years, two patients had inadequate sensing in the atrium and one patient had high pacing threshold. There were no lead dislodgement. In conclusion, these screw-in leads can be safely used in the atrium with acceptable pacing characteristics.