This paper raises questions about the discrete or continuous nature of rhythm classes. Within this framework, our study investigates speech rhythm in the different Arabic dialects that have been constantly described as stress-timed compared with other languages belonging to different rhythm categories. Preliminary evidence from perceptual experiments revealed that listeners use speech rhythm cues to distinguish speakers of Arabic from North Africa from those of the Middle East. In an attempt to elucidate the reasons for this perceptual discrimination, an acoustic investigation based on duration measurement was carried out (i.e. percentages of vocalic intervals (%V) and the standard deviation of consonantal intervals (∆C)). This experiment reveals that despite their rhythmic differences, all Arabic dialects still cluster around stress-timed languages exhibiting a different distribution from languages belonging to other rhythm categories such as French and Catalan. Besides, our study suggests that there is no such thing as clear-cut rhythm classes but rather overlapping categories. As a means of comparison, we also used Pairwise Variability Indices so as to validate the reliability of our findings.