The major use of fungicides is in the pre-and post-harvest prevention of the proliferation of pathogenic fungi in various food and fiber crops grown or stored under wann and humid conditions. The use of various fungicidal chemicals has escalated in the past decade, but, with the exception of two classes of chemicals, there has been little reason to associate fungicides with neurotoxicity in the human. They possess a low level of toxicity to most animal forms other than to fungi, their mechanisms of action being directed selectively toward the unique physiology and biochemistry of these organisms. The first exception, the dithiocarbamates, are closely related to the carbamic acid ester insecticides but show little ability to inhibit nervous tissue cholinesterases. Data related to human poisonings is quite limited, but cases of toxicity have occurred, although the mechanisms causing adverse health effects may be in dispute. In contrast, the second exception, the alkyl and aryl mercurial fungicides, have a long and tragic history relating to human poisonings, involving both individual cases and epidemics. While mercurial fungicides see little use in developed countries today, they are used extensively in the developing, equatorial nations, the locales of potentially greatest hazard to health because these chemicals are inexpensive to manufacture and are effective under the climatic conditions of use.