Sulfated-polysaccharides are exploited as antithrombotic and anticoagulant agents and suggested to be immunostimulants. The sulfated-polysaccharide isolated from the red-marine-algae Champia feldmannii (Cf-PLS) was purified by ion exchange chromatography and tested in experimental protocols of coagulation, inflammation (in Wistar rats) and nociception (in Swiss mice). Cf-PLS was tested i.v. for its anti-inflammatory activity in the paw-edema induced by classical inflammatory stimuli and s.c. for its pro-inflammatory activity in the paw-edema and peritonitis models. The anticoagulant activity was evaluated by the test of partial thromboplastin activation time (aPTT) and the antinociceptive effect in the writhing-test. Cf-PLS was not anti-inflammatory, but rather induced maximal edematogenic activity at 0.9 mg/kg (1.01+/-0.030 x 0.06+/-0.03 ml) compared to controls (0.06+/-0.03 ml), increased vascular-permeability (38.44+/-12.63 x 11.29+/-3.91 microg/g) and stimulated neutrophil migration (3.348+/-295 x 307+/-99 cells/microl) 1 h after injection. Cf-PLS was also antinociceptive (6.6+/-1.28 x 33+/-1.44 writhes) and extended human plasma coagulation time by 3 times. Our data suggest that this molecule may be an important immunostimulant.