Language barriers affect health care interactions. Large, randomized studies of the relative efficacy of interpreter modalities have not been conducted. To compare the efficacy of telephonic and in-person medical interpretation to visits with verified bilingual physicians. This was a prospective, randomized trial. The setting was an urban pediatric emergency department at which approximately 20% of visits are by families with limited English proficiency. The participants were families who responded affirmatively when asked at triage if they would prefer to communicate in Spanish. Randomization of each visit was to (1) remote telephonic interpretation via a double handset in the examination room, (2) an in-person emergency department-dedicated medical interpreter, or (3) a verified bilingual physician. Interviews were conducted after each visit. The primary outcome was a blinded determination of concordance between the caregivers' description of their child's diagnosis with the physician's stated discharge diagnosis. Secondary outcomes were qualitative measures of effectiveness of communication and satisfaction. Verified bilingual providers were the gold standard for noninferiority comparisons. A total of 1201 families were enrolled: 407 were randomly assigned to telephonic interpretation and 377 to in-person interpretation, and 417 were interviewed by a bilingual physician. Concordance between the diagnosis in the medical record and diagnosis reported by the family was not different between the 3 groups (telephonic: 95.1%; in-person: 95.5%; bilingual: 95.4%). The in-person-interpreter cohort scored the quality and satisfaction with their visit worse than both the bilingual and telephonic cohorts (P < .001). Those in the bilingual-provider cohort were less satisfied with their language service than those in the in-person and telephonic cohorts (P < .001). Using the bilingual provider as a gold standard, noninferiority was demonstrated for both interpreter modalities (telephonic and in-person) for quality and satisfaction of the visit. Both telephonic and in-person interpretation resulted in similar concordance in understanding of discharge diagnosis compared with bilingual providers. In general, noninferiority was also seen on qualitative measures, although there was a trend favoring telephonic over in-person interpretation.