Previous work reported by this laboratory showed that inorganic membranes such as stainless steel and ceramic microfilters were capable of rejecting anionic dyes and sodium nitrate from water solutions, It was of interest to see if this were possible with organic membranes such as propylene microfilters, Experimental data are presented showing that a polypropylene microfilter will reject both salt and Direct Red 2 from aqueous solutions when the conductivity of the solution is below 500 mu Siemens. The use of microfiltration to remove color is an important phenomenon considering that microfiltration comprises the largest fraction of the total membrane production in the world and is now used commercially for tertiary biological wastewater treatment. The effect of pH and salt concentration on the filtration rate and color rejection is also presented.