The γ-pyridone β-carboxylic acids or ‘quinolones’ rival β-lactam antibiotics in diversity of chemical structure and properties. Norfloxacin has a much wider spectrum than nalidixic acid which includes pseudomonas and Gram-positive cocci. It is also much more potent with MIC50 for Enterobacteriaceae of ≤0.06mg/l. This high activity is reduced in the presence of urine—possibly due to pH, but probably not to clinically inadequate levels. The results of laboratory tests from around the world are reviewed; despite various techniques these are remarkably consistent. The wide spectrum of norfloxacin should make it useful for therapy of urinary tract infection, and for gut decontamination and enteric infections. The high potency should allow use of lower doses with possibly less toxicity than nalidixic acid.