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Transcapillary escape rate of albumin was determined in 22 patients with different malignancies. In addition, urinary albumin excretion rate was measured in 24-h urine samples using a sensitive immunoassay. Increased urinary albumin excretion was defined as >/=20 microg/min according to conventional standards. Renal glomerular filtration and tubular function was estimated by 51Cr-EDTA plasma clearance and urinary beta 2-microglobulin, respectively. Median urinary albumin excretion rate was 15.0 microg/min (range 6-510 microg/min) and the frequency of increased urinary albumin excretion was 41%. This agrees with other studies showing increased albuminuria in several types of malignant diseases. Patients with advanced disease (tumour, node, metastasis (TNM) stage II-IV) had a significantly higher urinary albumin excretion rate than patients with localized disease (TNM stage I). Serum creatinine, glomerular filtration rate and urinary beta 2-microglobulin were all within normal limits. Median transcapillary escape rate of albumin was 5.5 %/h (range 2-8 %/h) and this level is comparable with values in healthy subjects. There was no significant difference in transcapillary escape rate between patients with elevated urinary albumin excretion and the normoalbuminuric group. Median value of the absolut outflux of albumin was 10.6 g/h with similar levels in patients with increased urinary albumin excretion and patients with normoalbuminuria. Our results indicate a high prevalence of minor glomerular dysfunction with a slightly elevated urinary albumin excretion in patients with malignancies. The normal endothelial function, as estimated by the transcapillary escape rate of albumin, suggests an overall unaffected capillary permeability and increased urinary albumin loss appears to be an isolated renal phenomenon in cancer patients.