Some English verbs use distinct forms for the preterite (e.g. I broke the door) and the past participle (e.g. I’ve broken the door). These verbs may variably show use of the preterite form in place of the participle (e.g. I’ve broke the door), which we call participle leveling. This paper contributes the first detailed variationist study of participle leveling by investigating the phenomenon in perfect constructions using data collected from three corpora of conversational speech: two of American English and one of British English. A striking degree of similarity is found between the three corpora in both the linguistic and the extralinguistic constraints on variation. Constraints on participle leveling include tense of the perfect construction, verb frequency, and phonological similarity between preterite and participle forms. The variable is stable in real time and socially stratified. The paper relates the findings to theoretical linguistic treatments of the variation, and to questions of its origin and spread in Englishes transatlantically.