Purpose: To verify the aesthetic impact of mild and moderate dental fluorosis on young adult students from the UFMG using pictures with different fluorosis levels simulated in a computer program. Materials and Methods: The sample consisted of 396 university students, randomly selected from various courses (except dentistry). These participants were shown three mouth pictures with different rates of dental fluorosis (TFO, TF2 and TF4) according to the Thylstrup-Fejerskov Index (TF). The volunteers gave an individual assessment of the pictures and graded them (from 1 to 10) based on their aesthetics. In addition, they answered if they would feel uncomfortable smiling and if they would seek dental treatment in each case. The results were submitted to a chi-square test (P 0.05). Results: The students preferred the TF4 picture to the TF2. The picture which presented no fluorosis was more often preferred than the pictures which presented some form of change due to fluorosis. Higher scores were recorded by men for the TF2 picture than by women (P 0.05). As for the TF0 and TF4 pictures, the scores were similar among males and females. Furthermore, women reported more discomfort in smiling (P = 0.001) and a greater desire to seek out dental treatment than did men. Only 27.5% of all students stated that they knew what dental fluorosis was. Conclusion: Mild and moderate dental fluorosis had a negative aesthetic effect on the studied population, leading to a strong desire to seek dental treatment to change the appearance of affected teeth. Keywords: aesthetic perception, dental aesthetics, dental fluorosis