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The activity of two chlorine derivates, sodium hypochlorite in water solution with NaCl (product A) and electrolytic chloroxidant (product B) has been tested in vitro against potentially human pathogenic fungi (Aspergillus niger, Aspergillus fumigatus, Microsporum gypseum, Candida albicans, Cryptococcus neoformans, Trichophyton mentagrophytes, Microsporum canis, Epidermophyton floccosum, Trichophyton rubrum, Sporotrix schenkii). For A. niger, the relation of the two compounds has also been considered between mycelial and sporidial forms. Dilutions used ranged from 0.15 to 10% (corresponding to 17.2-1150 ppm of active principle for product A, and to 18.3-1220 ppm of active principle for product B). These were applied for different times in order to assess the minimal inhibitory concentration (M.I.C.) and to evaluate the survival time of the microorganisms tested, which were strains from the collection of the Institute of Mycology, (Faculty of Agrarian Science, Perugia) and recently isolated ones from animal and vegetable tissues, cultivated on Sabouraud medium. The cell suspension to be tested was obtained on nutrient broth in shaken flasks (120 rpm) at 28 degrees C for 48 h, and was separated by centrifugation and 10000 rpm at 5 degrees C for 20 min, repeatedly washed with sterile physiologic saline and resuspended in sterile water where it was submitted to delicate pressure in order to fragment the mycelium. Activity tests were carried out on Sabouraud broth and Sabouraud agar with controls for every case without the active principle. Aliquots of the suspensions (microrganism++ + disinfectant) were transferred at regular intervals (1, 3, 5 and 10 minutes) to the two substrates in liquid and solid state, and the growth of microorganisms was followed at 28 degrees C for 48-72 h in the case of yeasts, and for up to 21 days in the case of sower growing fungi. The cell content of the different suspensions was found to range from 10(4) to 10(9) UFC/ml. The active chlorine contents of the two compounds was evaluated by iodometry simultaneously with the pH of the different solutions. Useful data were obtained from the comparison of the two systems of activity assessment of the fluid and agarized substrate. It was thus found that the two compounds were equally active against the species tested. Some of these (A. fumigatus, M. gypseum, A. niger, C. albicans, C. neoformans) were less sensitive to the compounds examined (doses for cell inactivation 0.62-2.5% for product A, and O.15-1.25% for product B) where at any rate product B was more active.(ABSTRACT TRUNCATED AT 400 WORDS)