Alginate, or irreversible hydrocolloid, is one of the most accepted impression materials used in dentistry. However, some substances existing in these materials can be toxic. The aim of this study was to assess the cytotoxicity of alginates for dental applications. Fourteen different alginates were assessed: Jeltrate, Jeltrate Plus, Jeltrate Chromatic, Alga Gel, Printer Gel, Ava Gel, New Print, Kromopan 100, Tropicalgin, Cavex Orthotrace, Hydrogum, Orthoprint, Cavex Color Change, and Qualitygel. Three control groups were also used in this study: positive control group (C+) consisting of cell detergent Tween 80, negative control group (C-) consisting of PBS, and cell control group (CC) consisting of non-exposed cells. After manipulating the materials according to the manufacturer&#8217;s instructions, samples were made by using silicone rings. Next, the samples were immersed into Eagle&#8217;s minimum essential medium (MEM) for 2 minutes followed by removal of supernatants and contact with L929 fibroblasts. After contact with the medium, the cells were incubated for further 24 hours in which 100? l of 0.01% neutral red stain were added. Cells were incubated again for 3 hours so that the stain could be absorbed. After this period, the cells were fixed and viable cell counting was performed by using a spectrophotometer (BioTek, Winooski, Vermont, USA) at wavelength of 492 nm. The results demonstrated statistical differences between CC and C- groups in relation to other ones (p<0.05). No statistical differences were observed between Jeltrate Plus and Hydrogum groups, between Jeltrate and Jeltrate Chromatic, Printer Gel, Tropicalgin, and Qualitygel groups, and between Jeltrate Chromatic and Alga Gel, Ava Gel, New Print, Kromopan 100, Cavex Orthotrace, Hydrogum, Orhtoprint, and Cavex Color Change groups. One can conclude, based on the results of this study, that all alginate materials were found to be cytotoxic.