The present study was done to compare the laser nephelometry with the latex agglutination test for the determination of rheumatoid factor. The following results were obtained. 1) The latex agglutination method was simple for qualitative tests but the nephelometry method was simpler and more accurate than the other for quantitative tests. 2) With the nephelometric method, endpoints were objectively assessed and standardization was easy. 3) In quantitative tests, the data were highly reproducible with the nephelometry method. 4) Both methods were generally similar in specificity and sensitivity but the nephelometry was more specific than the other in progressive and convalescent stages of the disease.