This study was carried out in the pulmonary department of a referral training hospital for thoracic medicine and surgery, with the aim of assessing the effects of pH and glucose level of a pleural effusion (PE) on survival and the response to pleurodesis (PD) with Corynebacterium parvum. A prospective study was carried out in 204 patients with recurrent, symptomatic PEs (73 benign, 131 malignant). Fifty eight per cent of 204 PEs had low pH (< 7.20; 7.01 +/- 0.14) nd glucose levels (< 60 mg.dL-1; 36 +/- 14 mg.dL-1), whereas the remaining 42% had higher pH (> or = 7.20; 7.36 +/- 0.07 and glucose levels (> or = 60 mg.dL-1; 79 +/- 16 mg.dL-1). PD was attempted twice with 7 mg of C. parvum injected through chest tube in all patients, who were then followed up for the outcome of PD and for survival from the time of PD until death or the closure of the study (August 1996). Of 204 cases, 201 were evaluable for survival and outcome of PD. In 91% of the low-and 82% of the high-pH/glucose benign PEs, complete PD was achieved while the corresponding values for the malignant PEs were 79% and 87%, respectively (p > 0.05). Six per cent of low-and 8% of high-pH benign PEs, and 13% of low- and 9% of high-pH malignant PEs were palliated with partial PD. Failures were 3% and 10% in the low- versus high-pH benign groups, and 8% and 4% in the low- versus high-pH malignancies, respectively. All 201 cases maintained the immediate post-PD outcome throughout the follow-up. Average survival was 21.8 months in high-pH benign PEs versus 21.1 months in low-pH benign PEs, and 9.9 versus 8.7 months, in high- and low-pH malignant PEs, respectively (p > 0.05). We deduce that, regarding survival and the response to pleurodesis with Corynebacterium parvum, there is no significant difference between low- and high-pH/glucose pleural effusions in malignant, or benign cases.