Cellulose is readily phosphorylated with phosphonic acid derivatives upon heating at elevated temperatures. In this paper, various properties of cotton fabrics phosphorylated with 1-hydroxyethylidene-1,1-diphosphonic acid, phenyl phosphonic acid, 2-carboxyeth ylphosphonic acid. and N-(phosphonomethyl)iminodiacetic acid are investigated. Phos phorylation occurs only in the presence of urea as expected. Without urea, there is discoloration as well as severe degradation of the fabric, as indicated by tensile strength reduction. Good reactivity is achieved by curing at 170°C for 2-4 minutes, and reaction efficiency is determined by phosphorus analysis. The best overall results are achieved with 1-hydroxyethylidene-1,1-diphosphonic acid. Although there is fabric discoloration upon curing with this agent, it is much less than that with the other derivatives. Discoloration upon curing of phosphorylated cottons is reduced by incorporating 1-4% dicyandiamide in the treatment formulation. Physical properties of the phosphorylated fabrics are dis cussed, along with thermogravimetric analyses of the substrates.