Working memory theory attributes the between-language difference in bilingual memory span to variation in speech rate and the time-based constraint of the phonological loop. We present two experiments examining the relationship between reading rate and memory span for Arabic numerals (e.g. 1, 2 and 3) and digit words (e.g. one, two and three) in both the languages of Spanish-dominant, Spanish–English bilinguals. The results of Expt 1 showed that reading time was shorter in Spanish than English for both numerals and digit words. Both number representations were read at equivalent rates in Spanish, whereas in English digit words were read faster than numerals. The results of the memory task indicated a larger span in Spanish than English and a span advantage for numerals compared to digit words in both languages. Experiment 2 replicated the findings of Expt 1 and the memory span advantage for numerals over digit words persisted for both languages under articulatory suppression. The present findings indicated the involvement of factors other than subvocal rehearsal in memory span tasks and, therefore, did not support a simple working memory theory explanation of the bilingual digit span effect.