Superlative adjectives accompanied by certain modal adjectives like possible (e.g. John bought the largest possible present) are ambiguous between a reading where possible is a regular noun modifier and a reading paraphrasable as ‘as Adj as possible’, called ‘modal superlative reading’. Three interesting restrictions have been observed in the literature. First, possible and some other adjectives ending in -able, but not potential and probable, support the latter reading. Second, when the modal adjective appears postnominally, only the modal superlative reading is (...) available. Third, prenominal possible needs to be in a local configuration to -est in order for the modal superlative reading to arise. Using LF structures independently motivated for degree constructions, the present paper develops a compositional semantic analysis of the modal superlative reading, makes correct new predictions concerning this reading, and—by reconciling previous, opposed syntactic analyses—allows us to derive the three empirical restrictions above. The key innovations are: (i) the previously proposed constituent [possible ▲ellipsis] is interpreted as an amount relative clause, and (ii) this constituent is treated as overtly expressing the comparison class argument of -est. (shrink)