PURPOSE: Current health literacy screening instruments for health care settings are either too long for routine use or available only in English. Our objective was to develop a quick and accurate screening test for limited literacy available in English and Spanish. METHODS: We administered candidate items for the new instrument and also the Test of Functional Health Literacy in Adults (TOFHLA) to English-speaking and Spanish-speaking primary care patients. We measured internal consistency with Cronbach's alpha and assessed criterion validity by measuring correlations with TOFHLA scores. Using TOFLHA scores <75 to define limited literacy, we plotted receiver-operating characteristics (ROC) curves and calculated likelihood ratios for cutoff scores on the new instrument. RESULTS: The final instrument, the Newest Vital Sign (NVS), is a nutrition label that is accompanied by 6 questions and requires 3 minutes for administration. It is reliable (Cronbach alpha >0.76 in English and 0.69 in Spanish) and correlates with the TOFHLA. Area under the ROC curve is 0.88 for English and 0.72 for Spanish versions. Patients with more than 4 correct responses are unlikely to have low literacy, whereas fewer than 4 correct answers indicate the possibility of limited literacy. CONCLUSION: NVS is suitable for use as a quick screening test for limited literacy in primary health care settings.