The monohaloacetic acids were reviewed, including information on occupational exposure, physical properties, toxicity, and structure/activity relationships. A detailed review and analysis was conducted of the biological effects of chloroacetic-acid (79118), sodium-chloroacetate (3926623), fluoroacetic-acid (144490), sodium-fluoroacetate (62748), iodoacetic-acid (64697), sodium- iodoacetate (305533), and bromoacetic-acid (79083). Topics included: human effects; epidemiologic studies; animal toxicity; diagnosis; antidotes; absorption, distribution, metabolism, and excretion; biochemistry; mutagenicity; carcinogenicity; and teratogenicity. Accurate information on the number of workers potentially exposed to these compounds was not available. Sodium- fluoroacetate has been widely used as a mammalian pest control agent. Although these compounds have different modes of action, all of them inhibit various metabolic pathways. Based on the acute toxicity to rats, fluoroacetate was the most toxic.