The book is devoted to the empirical study of Polish phonotactics. The research is conducted in the framework of Natural Phonology, which is a preference theory where clusters are placed on a continuum from the most to the least preferred ones. The character of the cluster is determined by the Net Auditory Distance Principle, which stems from the Beats-and-Binding model of phonotactics. The assumptions of this principle are compared with an earlier approach to studying cluster structure, i.e. the Sonority Sequencing Generalisation. The second dimension of the study is the role of morphology in cluster production and processing (hence morphonotactics). The assumptions of the Net Auditory Distance Principle, the Sonority Sequencing Generalisation and morphonotactics are verified in three areas of external evidence: first language acquisition, spontaneous speech of adults and phonotactic processing.