Myristamidopropyl dimethylamine [MAPD] is an amidoamine compound that shows activity against Acanthamoeba as well as a variety of other causal agents of microbial keratitis. MAPD, present in Opti-Free Express Multi-Purpose Disinfecting solution for contact lenses, has been shown to exhibit anti-acanthamoeba activity. Challenge test assays were used to study the efficacy of 50 mg/L MAPD against Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, Fusarium solani and Acanthamoeba polyphaga. MAPD gave a 3.7 log kill of P. aeruginosa after 60 min, 5.4 log for S. aureus by 45 min and 5 log for C. albicans and F. solani within 15 min. A. polyphaga cysts were reduced by 4 log within 120 min. MAPD also possesses excellent antifungal and antibacterial activity. MAPD may represent a broad-spectrum therapeutic antimicrobial for keratitis and surgical prophylaxis and deserves further evaluation in these roles. Myristamidopropyl dimethylamine uses and applications also include: surfactant; emulsifier for cosmetics and toiletries; conditioner; viscous builder; softener for textile finishes.