Speech rhythm is highly variable. Previous studies reported variability between languages, dialects, speakers, and labelers. Research further revealed an effect of sentence in the rhythmic characteristics of speakers of the same language. In the present study we tested whether the effect of sentence material is constant across varieties of the same language. We addressed this question by an example of analyzing rhythmic variability between eight dialects of Swiss German in three different sentences. Results showed a significant interaction for dialect*sentence for most of the tested rhythm metrics. We take this as evidence that differences between dialects are contingent upon the sentences used in the experiment. We further investigated which sources in the sentence material caused between-dialect differences in rhythm scores to vary. W e found exemplary evidence that dialect-specific phonological and morphological phenomena contained in the individual sentences are the prime suspects. Implications for future speech rhythm research are discussed.