Jungsoo Kim. 2022. A Corpus-Based Diachronic Investigation of the What About and How About Constructions. Studies in Modern Grammar 115, 77-117. This paper examines diachronic development patterns of the what about and how about constructions in American English, making use of authentic corpus data. Irregular wh-question constructions including the two, in general, have received much less attention than regular wh-question constructions and empirical studies on irregular wh-questions are scarce. In addition, previous literature has mainly focused on the similarities of the two constructions and has never discussed their diachronic development patterns. The findings of this corpus-based study show that the two constructions have undergone rather different development patterns for the past 200 years in American English. In particular, a fine-grained analysis of the diachronic development patterns of the two constructions based on their dependent categories reveals that it is worth investigating their diachronic properties about their preferred subtypes and illocutionary functions for each dependent category and that superficially similar distribution patterns indeed are statistically significantly different in most comparisons.