Using production and perception experiments, this study examined whether the prosodic structure inherent to telephone numbers in Tokyo Japanese affects the realization of focus prosody as well as its perception. It was hypothesized that prosodic marking of focus differs by position within the digit groups of phone number strings. Overall, focus prosody of telephone numbers was not clearly marked, resulting in poor identification in perception. However, a difference between positions within digit groups was identified, reflecting a prosodic structure where one position is assigned an accentual peak instead of the other. The findings suggest that, conforming to a language-specific prosodic\ structure, focus prosody within a language can vary under the influence of a particular linguistic environment.