The interpretation of bacterial cultures of the urine has been greatly aided by the use of quantitative methods. Analysis of the bacterial colony counts of urines obtained from large numbers of patients has indicated that, except for certain defined clinical circumstances,1a colony count greater than 100,000 per milliliter of freshly obtained urine generally indicates the presence of true bacteriuria, that is, of actual multiplication of bacteria within the urinary tract. Conversely, bacterial colony counts less than 100,000 usually represent contamination attendant upon the collection of the specimen.2,3 The validity of this approach has been amply confirmed,4-6despite some earlier and relatively minor disagreements that have since been largely resolved.7The quantitative approach has been of value not only in defining the presence or absence of infection of the urinary tract in the usual clinical setting, but also it has provided a means for determining the presence of asymptomatic infection