We used a concentric needle electrode (CNE) with 2 kHz low-cut filter and a single fiber electrode (SFE) in the same subjects for neuromuscular jitter measurement in the extensor digitorum communis (EDC) and orbicularis oculi (OOc) muscles. At the same session, 20 jitter values were obtained from each subject with each electrode. For EDC (during voluntary contraction), mean jitter values with SFE and CNE were 23.4 +/- 8 mu s and 23.3 +/- 8 us in 10 normals; and 56.8 +/- 28 us and 57.4 +/- 33 mu s in 10 myasthenics. For OOc (during electrical stimulation), mean jitter values with SFE and CNE were 17.9 +/- 5 mu s and 16.3 +/- 4 mu s in 11 normal subjects, and 41.2 +/- 29 mu s and 36.7 +/- 27 mu s in 10 myasthenics. For both muscles, the numbers of individual abnormal jitter values with SFE and CNE were highly comparable. Both needles labeled the same patients as having "normal" or "abnormal" neuromuscular transmission. CNE may be an alternative to SFE in neuromuscular jitter analysis. (C) 2000 John Wiley & Sons, Inc.