Purpose: The authors assessed adult selective auditory attention to determine effects of (a) differences between the vocal/speaking characteristics of different mixed-gender pairs of masking talkers and (b) the rhythmic structure of the language of the competing speech. Method: Reception thresholds for English sentences were measured for 50 monolingual English-speaking adults in conditions with 2-talker (male-female) competing speech spoken in a stress-based (English, German), syllable-based (Spanish, French), or mora-based (Japanese) language. Two different masking signals were created for each language (i.e., 2 different 2-talker pairs). All subjects were tested in 10 competing conditions (2 conditions for each of the 5 languages). Results: A significant difference was noted between the 2 masking signals within each language. Across languages, significantly greater listening difficulty was observed in conditions where competing speech was spoken in English, German, or Japanese, as compared with Spanish or French. Conclusions: Results suggest that (a) for a particular language, masking effectiveness can vary between different male-female 2-talker maskers and (b) for stress-based vs. syllable-based languages, competing speech is more difficult to ignore when spoken in a language from the native rhythmic class as compared with a nonnative rhythmic class, regardless of whether the language is familiar or unfamiliar to the listener.