Proeedures are developed for the determination of fluorine and phosphorus in poly-mers and organic compounds iby titration with Nd(NO3)3-EDTA after decomposing the sample by O-flask．An amount of sample eorresponding to approximatoly 1 mg of flu-orine is decomposed and absorbed in an O-flask containing an excess of 0.01 M Nd3+ (NO3)3．The absorbing liquid is boiled for 3 minutes．After being allowed to eool，a pH=5.5 buffer is added．In the presence of xylenol orange．the mixture is titrated with 0.01 M EDTA．The proeedure for determining phosphorus is the sanle as described above．hut preeipitation reaction of NdPO4 is earried out in pH 5.5 after eliminating CO2．If sam-ple contains F and P，PO43-in the solution containing F- can be detemined after eli-minuting F- by adding HNO3 and concentrating solution to dryness，and the percenta-ge of F can be found after determining the total content of F and P．Determinetion procedure of total content is the salne as F-，but buffer is added while the mixture is hot．The maximum error of determing P is±0.20％ and F is+0.30％ except high flu-orine or fully flucrinated eompmmds which give values approximately 0.50％ lower than calculation．