Purpose: The current study was an attempt to provide initial evidence on how to predict the optimal language in which to conduct speech perception testing for Spanish/English (S/E) bilingual listeners. Method: Thirty normal-hearing S/E listeners differing in age of language acquisition, length of immersion, daily language use, self-rated listening proficiency, and language dominance were evaluated on the English and Spanish word recognition tests in quiet and in speech-spectrum noise. Results: Performance on the English and Spanish tests was not correlated for any conditions. English word recognition was most significantly correlated with age of English acquisition. Logistic regression analyses further demonstrated age of English acquisition to be a good predictor of listeners' relative success on the 2 tests in quiet and at +6 dB signal-to-noise ratio (SNR). At 0 dB SNR, language dominance had the highest predictive specificity, whereas the combination of age of English acquisition and Spanish listening proficiency had the highest sensitivity. Conclusions: A Spanish word recognition test would likely yield more favorable results for S/E bilingual listeners who were Spanish-dominant or who acquired English at 10 years of age or older. It may be necessary for listeners who acquired English at 7-10 years of age to be evaluated in both English and Spanish.