From a historical perspective, punctuation marks are often assumed to only represent some of the phonetic structure of the spoken form of that text. It has been argued recently that punctuation today is a linguistic system that not only represents some of the phonetic sentence structure but also syntactic as well as semantic information. One case in point is the observation that the semantic difference in differently punctuated parenthetical phrases is not reflected in the intonation contour. This study provides the acoustic evidence for this observation. Furthermore, this study makes recommendations to achieve natural-sounding text-to-speech output for English parentheticals by incorporating the study's findings with respect to parenthical intonation. The experiment conducted for this study involved three male and three female native speakers of Canadian English reading aloud a set of 20 sentences with parenthetical and non-parenthetical phrases. These sentences were analyzed with respect to acoustic characteristics due to differences in punctuation as well as due to differences between parenthetical and non-parenthetical phrases. A number of conclusions were drawn based on the results of the experiment: (1) a difference in punctuation, although entailing a semantic difference, is not reflected in the intonation pattern; (2) in contrast to the general understanding that parenthetical phrases are lower-leveled and narrower in pitch range than the surrounding sentence, this study shows that it is not the parenthetical phrase itself that is implemented differently from its non-parenthetical counterpart; rather, the phrase that precedes the parenthetical exhibits a lower baseline and with that a wider pitch range than the corresponding phrase in a non-parenthetical sentence; (3) sentences with two adjacent parenthetical phrases or one embedded in the other exhibit the same pattern for the parenthetical-preceding phrase as the sentences in (2) above and a narrowed pitch range for the parenthetical phrases that are not in the final position of the sequence of parentheticals; (4) no pausing pattern could be found; (5) the characteristics found for parenthetical phrases can be implemented in synthesized speech through the use of SABLE speech markup as part of the SABLE speech synthesis system. This is the first time that the connection between punctuation and intonation in parenthetical sentences has been investigated; it is also the first look at sentences with more than one parenthetical phrase. This study contributes to our understanding of the intonation of parenthetical phrases in English and their implementation in text-to-speech systems, by providing an analysis of their acoustic characteristics.