Background/Aim: Heparin has been shown to be renoprotective in a number of experimental nephropathies. The inflammatory component in the early phase of Adriamycin (ADR) induced nephropathy has been established. A microdose of low molecular weight heparin (Fragmin; F) has been noted to exert immunomodulatory effects independent of its anticoagulant activity. We assessed the effects of microdoses of F on daily proteinuria and glomerular production of tumor necrosis factor alpha (TNF-α) and prostaglandins 8 and 15 days after induction of ADR nephropathy. Methods: Following intravenous injection of ADR (7 mg/kg) to Wistar rats weighing 200 ± 20 g, F 20 µg/day/rat s.c. was administered for 8 and 15 days (groups F8 and F15). The respective control groups (C8 and C15) received normal saline subcutaneously. Proteinuria, serum albumin, and creatinine clearance were evaluated on days 8 and 15. The production of TNF-α and prostaglandins from glomerular supernatants was measured by radioimmunoassay on days 8 and 15. Results: F significantly reduced proteinuria (mg/day) on day 8: 13.6 ± 1.2 in F8 versus 40.3 ± 2.7 in C8 (p = 0.008). The glomerular production of TNF-α (pi/ml) was significantly lower on day 8 in rats treated with F: 356 ± 33 in F8 versus 764 ± 81 in C8 (p = 0.006). A decrease in the prostaglandin E<sub>2</sub>/thromboxane B<sub>2</sub> ratio was noted in the F group between 8 and 15 days (1.1 in F8 vs. 0.9 in F15, p = 0.005) which principally reflects an increase of thromboxane B<sub>2</sub>. The antiproteinuric effect of F shown after 8 days was no longer present after 15 days (354 ± 91 mg/day in F15 vs. 499 ± 69 mg/day in C15, p = 0.33). The same trend was seen for the glomerular production of TNF-α. Light microscopy and immunohistochemistry for interstitial and glomerular macrophages were negative. Conclusion: The lowering effect of microdoses of F on the proteinuria seen during the early phase of ADR nephropathy may be mediated by a decreased production of glomerular TNF-α, supporting the anti-inflammatory action of low molecular weight heparin.