Aims: To evaluate the antimicrobial efficacy of a novel u.v. beaker, powered in a domestic microwave oven. Methods and Results: Three beakers were compared, with most rapid killing obtained in the Neutra Plasma 50(TM). Ultraviolet light generated within the beakers efficiently killed planktonic and surface-associated Streptococcus mutans, Pseudomonas aeruginosa, vegetative Bacillus stearothermophilus, herpes simplex and polio viruses. Candida albicans and Mycobacterium phleii were less rapidly killed, and only 70% inactivation of B. stearothermophilus endospores was achieved. Irradiation for 45 s reduced viable bacterial counts in saliva by > 99%. Conclusions: The u.v.-generating beakers efficiently reduced viable counts of bacteria, yeast and viruses. Kinetics of killing varied, reflecting the fact that lethal mechanisms are complex, and probably depend on interplay between u.v. and heat. Significance and Impact of the Study: This novel method of generating u.v., using a cheap and widely available power source, provides a rapid, inexpensive and non-toxic method of disinfection with a wide range of applications in hospitals, clinics and the home.