For /h/ in Modem Korean phonology, the explanation to the phenomena of obstruent-like behaviors like tensification of consonants followed by /h/ or nasal assimilation of /h/ at verb stem-final position in spite of its phonetic nature has been the greatest issue. Classifications of it in terms of phonemic status and the aspiratedness have been the next ones. This paper dealt with these three issues for the purpose of shedding some light on them. The results are as follows: First, /h/ is classified to a vowel phonetically. But, phonemically, it is a kind of vowel(liquid). Second, /h/ is an aspirated sound both phonetically and phonemically. Third, the best explanation to the phonological behaviour of verb stem-final /h/ is the multiple underlying forms of the verb stem. Multiple underlying form is a device of concrete phonology, which bans unnatural explanations like abstract underlying forms or extrinsic rule ordering by accepting some unnatural phenomena as they are. Multiple underlying form suggested here dates back to Middle Korean age, and it could be supported by many cases in Modem Korean dialects as well.