Cytochalasin A is one of a family of potent mycotoxins produced by several species of fungi. All members of the class exhibit profound effects on cytoskeletal proteins, giving rise to pronounced morphogenic activity in animals and plants. Like most cytochalasins, cytochalasin A exhibits potent inhibition of actin filament function leading to cell death by apoptosis and displays a broad range of resultant cellular actions. Despite the common mode of action, there is evidence that individual members of the class display diverse selectivity. Specifically, cytochalasin A is one of the few cytochalasins active against HIV-1 protease.