This chapter addresses a number of issues relating to rhythm categorization behaviour. Experimental and theoretical work on categorical perception is characterized by a vast diversity of approaches. Two main category types, sensory perception and generic knowledge categories, outline two corresponding broad areas of research on category cognition. A more detailed mapping of the resultant perceptual rhythm-space was performed by the calculation of goodness-rating means and the corresponding standard error for all variations within each category. An illustrative example of categorical perception can be drawn from the domain of colour perception. The accepted experimental approach to demonstrating categorical versus non-categorical perception is psychophysical and it is based on identification and discrimination tasks. Contemporary theories of musical rhythm have stressed the importance of approaching musical rhythm patterns as multilevel structures, which are actually shaped by the interaction of various durational relationships between their different time levels.