Muscle fiber conduction velocity (MFCV) estimation from surface signals is widely used to study muscle function, for example in neuromuscular disease and in fatigue studies. However, most analysis methods do not yield information about the velocity distribution of the various motor unit action potentials (MUAPs). We have developed a new method - the Interpeak latency method (IPL) - to calculate both the mean MFCV and the spread of conduction velocities in vivo, from bipolar surface EMG during isometric contractions. Surface EMG was analyzed in the biceps brachii muscle in 15 young male volunteers. The MUAP peaks are automatically detected using a computer program. Associated peaks are used to calculate a mean MFCV and the standard deviation (SD). The SD is taken as a measure of the MFCV spread. The main finding is that the IPL-method can derive a measure of MFCV spread at different contraction levels. In conclusion, the IPL-method provides accurate values for the MFCV and additionally gives information about the scatter of conduction velocities.