In a study of 5,571 patients from the general surgery departments of 11 Israeli hospitals, the crude overall wound infection rates showed interhospital heterogeneity. The rates ranged from 6.3% to 12.4% (P(X2) = 0.039). Controlling for the different distributions of procedures performed in the various institutions did not reduce this variability. None of the hospitals had either consistently high or consistently low infection rates. A hospital could have low rates for one procedure and high rates for another. Therefore, the decision was made to proceed with procedure-specific analyses. This article details results of the analysis of 1,487 hernia operations. Four variables (old age, infection at another site, incarceration, and introduction of drains) accounted for almost all the differences in infection rates among the institutions. Of the four, presence of drains had the strongest association with infection (P derived from the logistic model <0.001). The risk was consistent in all hospitals and was unconfounded by other measurable factors. In contrast, the pattern of using drains seemed arbitrary and inconsistent, ranging from 9% of patients in one hospital to 41% in another. These findings were used as a basis for discussion with the surgical teams and for the initiation of a randomized clinical trial on the use of drains in hernia operations.