Although it is broadly accepted that adult second-language (L2) learners focus attention only on those aspects of sounds needed for phonemic contrast, the role that allophony plays in the process of L2 speech learning is less well understood. It is widely assumed that speakers do not have conscious awareness of and access to first-language (L1) allophones. This study experimentally tested whether L2 learners have access to their L1 allophonic inventories and whether they can access this phonological knowledge to employ it in L2 speech production in order to reach relatively native-like L2 pronunciation. The study analyzed the ability of twelve adult native English speakers acquiring Spanish to produce phonetically similar sounds that have different phonological relations and distributional properties in their respective L1 and L2. Data collection consisted of the participants reading aloud a list of stimuli containing target sounds [eth] and [r] in four sets of repetitions. A perceptual, spectrographic, and statistical analysis of the data was performed. The results suggest that access to L1 allophones is perhaps limited and dependent on some other variables (e.g., L1 orthography, the stage of L2 phonological acquisition, functional load of the target sound, motivation), but it is not impossible. (Contains 10 tables, 2 figures and 7 notes.)