Contamination of fluorescein solutions by Pseudomonas aeruginosa has been a concern of ophthalmologists for many years because of the severity of pseudomonas keratitis. Attempts to prevent contamination have been directed at stringent sterility control during manufacture and the introduction of single-dose disposable containers such as Minims. Deliberate contamination of Minims fluorescein with Pseudomonas aeruginosa was attempted. Under conditions likely to be met with in clinical practice the contents remained sterile. However, under extreme conditions of immersion in pure broth culture of Pseudomonas aeruginosa contamination could be achieved. The relevance of these results to clinical practice is discussed.