This article accounts for various factors triggering /h/-dropping in the word-initial consonant clusters hr-, hl-, and hn- such as ease of articulation, acoustic and auditory weakness, universal preference (CV syllable structure), and French influence (no word-initial /h/). It also provides a constraint-based account of the developmental process of /h/-dropping, assuming that /h/-dropping would have happened under the scenario on the basis of the interaction of bottom-up and top-down processing in speech perception. /h/-dropping in consonant clusters seems to have proceeded like this: [hr], [hl], [hn] > [hr]∼[r̥], [hl]∼[l̥], [hn]∼[n̥] > [r̥]∼[r], [l̥]∼[l], [n̥]∼[n] > [r], [l], [n]. In analyzing these diachronic sound changes, I have presented two markedness constraints (*SONvl and *[+s.g., +glottal]) and two faithfulness constraints (DEP-IO and MAX-IO). The diachronic changes could reasonably be accounted for through four stages. The constraint ranking of the first stage is DEP-IO, MAX-IO, *SONvl >> *[+s.g., +glottal], that of the second stage is DEP-IO, MAX-IO >>>> *SONvl, *[+s.g., +glottal], that of the third stage is DEP-IO, *[+s.g., +glottal] >>>> *SONvl, MAX-IO, and that of the last stage is DEP-IO, *[+s.g., +glottal], *SONvl >> MAX-IO.