A turbidimetric micromethod for estimation of fibrinogen, both manual and by automatic analysis, is described. It is based on the use of a reagent containing ammonium sulphate, EDTA and glycerol. The blood may be collected either on heparin, EDTA or trisodium citrate. The correlation with the weight methods (r = 0,980), chronometric methods (r = 0,939) and immunonephelemetric methods (r = 0,985) permits its use as a routine method.