Report was made on the general methods of determination of arsenic and some problems were pointed out in their application relative to the cosmetic materials and products, that is, factors contributing to the plus and minus effects for determining As. One of the minus effect studied iron oxide and good results were obtained as follow:i) The silver diethyldithiocarbamate method for determining As in one gram of iron oxide:After dissolving one gram of iron oxide with HC1 and HC1O3, the solution is evaporated to near dryness, converted Fe3+ to Fe2+ by reducing with NH2OH-HC1 salt, using special arsine evolution apparatus (fig I), microamount of As in commercial iron oxide was determined spectrophotometricaly at 540mμ with silver diethyldithiocarbamate in pyridine within the following coefficient of variation: 1.8% (10.5ppm): 21.8% (0.4ppm) and the effect of deverse metal, 80μg Sb, 100mg Pb does not have any ill effect.ii) Gutzeit Method:Standerlized pretreatment is necessary for obtaining consistent results by this method and compared favorably with the spectrophotometric method as described in i).iii) Square-wave polarography method:In 2N hydrochloric acid solution, two waves have been separated clearly. The shape of the second wave is better than the first, and was scarcely effected by various metalic ions.By using the benzene extraction at the concentration of H2O:HC1=1:10 level or higher, As3+ and As5+ may be determined quantatively by treating with benzene-HC1 and benzene-HC1-HBr extraction.In conclusion, it is our earnest hope that a standardized method of pretreatment and the maximam limits of arsenic contents for cosmetic products should be settled.