AbstractWe investigate the influence of the prosodic structure of German as first language (L1) on the application of thespirantization rule in Spanish as a second language (L2). According to the Prosodic Hierarchy, the prosodic domains in whichphonological rules apply may vary according to whether the language has a grouping tendency or not. While Spanish spirantization(where /b d g/ are produced as [β ð ɣ] after continuant sounds) applies across the Intonational Phrase (IP), German restrictsgrouping processes to smaller domains, the largest of them being the phonological word (pword). We hypothesized that L1 Germanlearners of Spanish apply spirantization progressively, starting from the pword. Twenty-six participants were recorded reading twotexts with instances of /b d g/ within foot, pword, and IP. Results support that L1 German learners of Spanish spirantize mainlywithin feet, and less so within pwords and IPs; furthermore, consonants /b — d/ are more likely to be spirantized than /g/ acrossall contexts by more proficient learners. We conclude that the starting point of spirantization is not the largest one licensed bythe learner’s L1, but that there is an L1-independent path where learners start from the smallest domain in the hierarchy.