This paper presents a linguistic discussion of play-languages--designated as ludlings by the author and tentatively defined as the result of a transformation or a series of transformations acting regularly on an ordinary language text, with the intent of altering the form, but not the content of the original message, for purposes of concealment or comic effect. Based on the types of phonological transformations operating in the creation of a specific ludling, i.e., expansion, contraction, substitution, rearrangement, or a combination of two or more of these mechanisms (polysystemic), the author establishes a typology and presents examples for each type. The author contends that the study of ludlings and their formation gives valuable information on the native speaker's intuition as to what constitutes a syllable, a vowel, a consonant, a consonant cluster, a word, or a suprasegmental; such study also indicates which phoneme sequences may be permissible in the language. (VM)