Arsenic acid (H(3)AsO₃) is a harvest aid chemical used in Texas and Oklahoma to desiccate cotton (Gossypium hirsutum L.) in preparing for stripper harvesting. This desiccant is annually used to prepare over one million acres of cotton for harvest in Texas. In 1989, fines were levied against a cotton finishing plants that had arsenic (As) in wash water above acceptable tolerances. It was determined that cotton being used was from stripper harvested areas of Texas where arsenic acid was used as a desiccant. To address this problem, twelve field studies were conducted in 1989 and 1990, six each year, in various regions of Texas to evaluate the effects of arsenic acid desiccant treatments on arsenic residues on lint Treatment variables included location (environment), desiccant rates, pre-treatments with a boll opener and defoliants, and methods of application. Bur cotton samples were hand harvested from the plots just prior to the application of arsenic acid, one or two times after treatments were applied, and at harvest. Lint samples were also collected from bales of cotton harvested from individual plots. Hand harvested samples were ginned to obtain lint, seed, and bur (gin trash) fractions. All lint samples were analyzed for residual arsenic (As) at the USDA Cotton Quality Research Station, Clemson, SC. Selected bur and seed samples were tested for residual As at ENRECO Laboratories, Amarillo, Texas. Some variability in detectable As within samples was noted in all three fractions (lint, burs, and seed) but was generally highest in the lint fraction. Levels of residual As in lint were primarily influenced by the rate of arsenic acid applied, rainfall after treatment, and defoliation prior to chemical desiccation. In five of the six trials, As residue levels in burs were typically lower than those in the lint. Exceptionally high levels of As were detected in the bur fraction from plots where the desiccant was applied via helicopter. Rainfall reduced As residue levels in the burs but not to the same extent as in the lint Arsenic residues on the seed averaged only 3.6 ppm (detection limit of ± 1.5 ppm). Test results from 1989 and 1990 showed that arsenic acid rates, defoliation, and post treatment rainfall influenced arsenic residues on cotton lint and burs. Defoliation tended to increase As deposition on lint and burs whereas even small amounts of rainfall reduced residue levels in both. Arsenic residues in cotton treated with labelled rates of arsenic acid were high enough in some instances to produce As concentrations in wash water of up to 0.7 ppm, which is above levels permitted in discharge water in many areas. Producers can minimize As residues on lint by strictly adhering to labelled use rates of arsenic acid These use rates cannot be lowered without adversely affecting the efficacy of the acid in desiccating cotton. Ultimately, manufacturers that utilize large volumes of stripper cotton should consider utilization of technologies that precipitate and remove As from water during the washing process. This problem presents a challenge to industry, cotton producer organizations and public research institutions to develop and foster the adoption of such technology to alleviate public concerns about arsenic residues in the environment as well as in cotton apparel.