Introduction. Iodine based products have been and are still used in medicine as disinfectant or antiseptic substances, because of their bactericidal, sporicidal, protocidal and disinfection effect. Algaecide effect has been less studied and represents a strong motivation for this study. Aim. This paper is aiming to test the sensitivity to iodine based products of unicellular algae of the genus Prototheca. Such products might be used for the treatment of diseases involving these pathogens.Materials and methods. A total number of twenty-two Prototheca zopfii strains isolated from cows with mastitis or bovine shelters, were tested within this study. The algal strains were identified based on morphological characteristics (shape, size, presence of endospores), cultural (liquid and solid media characteristics) and biochemical (fermentation of sugars). Prototheca wickerhamii ATCC 16529 reference strain was also included in the evaluation. Iodinated products used were represented by: Lugol solution, iodine tincture, betadine, videne and potassium iodide. Determination of the inhibitory effect was measured by diffusion technique in agarose gel and by liquid medium dilution method. For the tincture of iodine and betadine, the inhibitory effect was also appreciated in relation with the time of contact (5, 10, 15, 30 and 60 minutes).Results. By the agar diffusion technique, it was found that inhibition zones varying sizes were correlated with the composition of those products. For the 22 Prototheca zopfii tested strains, the size of inhibition areas was within the following values (average diameter): iodine tincture 25.71 mm, betadine 26.4 mm, videne 25.61 mm, Lugol’s solution 11.33 mm and potassium iodide 11.14 mm. For Prototheca wickerhamii strain inhibition areas had the following values: betadine 26 mm, iodine tincture 24 mm, videne 24 mm, Lugol’s solution 10 mm, potassium iodine 14 mm. In case of different contact times meant to establish the algaecide effect - occurred in the first 5 minutes of contact, for both iodine tincture and betadine.Conclusion. Iodine based products tested showed inhibitory effect on algal strains. The best efficacy was found for betadine and iodine tincture (pharmaceutical/commercial products). The inhibitory effect occurs in the first 5 minutes of contact. There was no resistance phenomenon nor the presence of resistant colonies in the inhibition zones.