The aim of the present study is to conduct a comprehensive corpus analysis of the constituent order of main declarative clauses with the interjection hwæt ‘what’ in the clause-initial position in Old English prose texts. On the basis of his analysis of Ælfric's Lives of Saints and Bede's Historia Ecclesiastica, Walkden (2013) claims that such hwæt-clauses pattern with subordinate clauses with respect to their verb position. My study confirms Walkden's basic empirical findings that hwæt-clauses do not behave like typical main clauses as far as their constituent order is concerned. However, there are numerous differences between them and subordinate clauses introduced by hwæt, that is, free relatives and embedded questions. The analysis suggests that the conditions favoring the use of the V-final order in main hwæt-clauses resemble the ones identified for ordinary V-final main clauses in Bech 2012. What is more, the study shows that the functional differences between hwæt- and hwæt þa-clauses noted in Brinton 1996 are blurred in Old English prose because of a regular variation between hwæt þa-S and hwæt-S-þa patterns. The data also suggest that þa in hwæt þa-clauses should rather be analyzed as an independent clause element.