Abstract: The synthesis of three new trisazo dyes containing 4,4'-diaminobenzanilide as middle component is presented. The dyes were analyzed by thin layer chromatography (TLC), electronic spectra (VIS) and their structure was confirmed by mass spectroscopy (FABS). The toxicity of the synthesized dyes was evaluated by biological tests, using the process of metamorphosis in the marine Hydrozoon Hydractinia echinata. The concentration (termed by MRC50) at which the synthesized dyes (and their precursors) antagonize metamorphosis induction was determined. The obtained results indicate that these dyes exhibit toxicity values which are lying in a low average lows scale of toxicity.