BackgroundAntimicrobial resistance is an increasing problem in developing countries and antibiotic use is widespread. Our previous surveys in Java, Indonesia, revealed that most antibiotic use was probably unnecessary or ineffective. The aim of this study was to explore a potential connection between resistance and substandard antibiotics sold in the area.MethodsA cross-sectional field study using the simulated client method was conducted in Surabaya. Five first-line antibiotics were requested with or without prescription (OTC). A certified laboratory analysed the drug content using validated methods. Possible determinants of substandard quality were explored.ResultsIn total, 104 samples from 75 pharmacies, ten drug stores and 39 roadside stalls (kiosks) were obtained. Pharmacy employees filled all OTC requests. Three quarters of kiosks sold antibiotics. Antibiotics were dispensed as single blister strips or repackaged (16%) without label. Ninety five percent of samples carried the label of 14 Indonesian manufacturers. The pharmaceutical quality did not meet BP standards for 18% of samples. Deviations (less active ingredient) were small. There was no association between low content and type of outlet, sold with or without prescription, registration type, price or packaging. Median retail prices of products carrying the same label varied up to 20 fold.ConclusionsAntibiotics were available OTC in all visited pharmacies and sold in the streets of an Indonesian city. Most samples contained an active ingredient. We urge to increase enforcement of existing regulations, including legislation that categorizes antibiotics as prescription-only drugs for all types of medicine outlets, to limit further selection of antimicrobial resistance.