To my knowledge, it has not been reported that Korean employs 'what'-exclamatives. In this study, I argue that a *mwe-l*-{*ku*/*i*}*lehkey*-clause like *mwe-l kulehkey pissan-cha-lul sass-e!* is recognized as a 'what'-exclamative. The *mwe-l*-exclamative expresses a violation of the speaker's expectations and receives only a degree interpretation (as argued by Rett 2011 for English exclamatives). I propose that a *mwe-l*-clause denotes a maximal degree obtained by a maximality operator *kulehkey*. Given that the content of *mwe-l*-exclamatives can be denied (cf. Rett 2011) and that they can be used as responses to information-seeking questions (cf. Grimshaw 1979, Zanuttini & Portner 2003), I analyze *mwe-l*-exclamatives as expressing assertive speech acts. To capture this speech act, I argue that the maximal degree denoted by the *mwe-l*-clause serves as an input to an assertive force operator, Excl-Op. The operator takes a maximal degree and returns the proposition that the maximal degree exceeds (or meets) a contextually provided standard established by the speaker's expectations. Last but not least, *mwe-l*-exclamatives are intriguing in that depending on context, the speaker evaluates the assertive content as positive or negative. To capture this, I argue that *mwe-l*-exclamatives involve an evaluative operator. This operator takes the assertive content expressed by Excl-Op to express the speaker's evaluative attitudes about it.