The response of the fourth instar larvae of Culex pipiens to three photosensitizing dyes (Rose Bengal, phloxine B and rhodamine B) was investigated under laboratory conditions. The mortality percentages increased as the concentrations and exposure times of all tested dyes increased. As judged by a comparison of median lethal concentration values, Rose Bengal was the most effective dye followed by phloxine B, then rhodamine B. Treatment fourth instar larvae with different concentrations of three tested dyes induced morphological changes and aberrations in larval stage. In the current study, based on median lethal time values, Rose Bengal had the lowest time values and fastest action compared to other tested dyes. Results also revealed that the addition of non- toxic concentrations of both tween 20 and tween 60 to median lethal concentration of Rose Bengal showed no significant changes and didn't appear synergism to their efficacies compared to Rose Bengal used alone.