The Blairex Water Purifier (previously called The Blairex Deionizer) is a filtration unit designed to purify tap water for uses that require distilled or deionized water. The unit is intended to offer soft contact lens wearers a more convenient and safe method of obtaining distilled water when using salt tablets or enzymatic cleaning tablets. In this study, the safety of these units was analyzed from a microbiological point of view. The microbial starting state of 18 factory sealed Blairex Water Purifiers was evaluated by filtering sterile water through each unit and enumerating the organisms in the effluent. Then a known number of specific microorganisms was filtered through each unit. For the next 30 days, subsequent sterile distilled water filtrations were done each day. The effluent was collected with each filtration and enumerated for microorganisms. The results indicated that the majority of Blairex units tested were not sterile from the onset. Several Blairex units evaluated did support bacterial growth, as the bacteria that were passed through the unit on day 1 of the study were found in the effluent in increasing numbers with use. The clinical implications of our findings are discussed. Each time Blairex units were obtained for evaluation, the units appeared different in either filter attachments, plastic composition, or shape. The results varied according to which type of Blairex unit was tested.