We compared the diagnostic value of quantitative cultures of bronchoalveolar lavage (BAL) and telescoping plugged catheter (TPC) samples in 40 patients with moderately severe community-acquired pneumonia (CAP). None had received antibiotics previously. BAL quantitative cultures were performed in 13 control patients without pneumonia. In 28 (70 percent) patients, TPC cultures yielded > or = 10(3) cfu/ml of a pathogenic bacterium in pure culture. In 27 of these cases and in four additional cases, BAL cultures yielded > or = 10(3) cfu/ml. BAL cultures from the control group were sterile in seven cases, yielded normal flora in three cases, and yielded microorganisms thought to be not significant in two cases. Microbiologic agreement was reached by both TPC and BAL for 32 (84 percent) of 38 microorganisms recovered. Quantitative cultures from both techniques correlated very well (r = 0.71, p < 0.0001). We conclude that both TPC and BAL have similar accuracy to determine etiologic diagnosis of CAP. There was good qualitative and quantitative agreement between both techniques.