Objective: We describe the performance of Single Item Literacy Screener (SILS) questions, and educational attainment, as screening for inadequate health literacy (IHL) in older monolingual Spanish speakers. Design: We used a cross-sectional design, interviewing participants once at the time of their arrival for a clinic appointment. Setting: We conducted this study in primary care and geriatrics clinics in an urban US safety-net hospital. Method: We conducted in-person interviews with older monolingual Spanish-speaking diabetes patients, comparing responses to three SILS questions, and education, to shortened Test of Functional Health Literacy in Adults (sTOFHLA) scores. We calculated sensitivities, specificities and areas under the receiving-operator characteristic (AUROC) curve. Results: We interviewed 160 patients--134 (84%) had IHL by sTOFHLA scores. The best performing SILS question, "How confident are you filling out medical forms by yourself?" had an AUROC curve of 0.82 (95% CI 0.75-0.89). Using this question's most stringent cut-off, sensitivity was 0.93 (95% CI 0.89-0.97); specificity was 0.27 (95% CI 0.20-0.34). The other two SILS questions had AUROC curves less than 0.50. The educational achievement AUROC curve was 0.88 (95% CI 0.78-0.97); using an education cut-off of six years or less had a specificity to 0.81 (95% CI 0.75-0.87) and sensitivity of 0.83 (95% CI 0.77-0.89). Conclusion: Clinicians and investigators considering using single items as screeners for IHL in older US monolingual Spanish speakers should either use the "confidence with forms" SILS, being aware of its specificity limitations, or a single question assessing educational achievement. (Contains 2 tables and 2 figures.)