Background <p>The use of autologous fat tissue is one of the common methods among plastic surgeons for cosmetic and reconstructive problems. One of the drawbacks of these techniques is the decrease in the efficiency of post-harvest fat cells. This study aimed to investigate the effect of fat storage time at room temperature on the viability of suctioned fat cells.</p> Methods <p>In this prospective study, 15 patients who were candidates for liposuction (abdominoplasty and abdominal &amp; flank liposuction) who met the inclusion criteria were evaluated. The adipose tissue of these patients was stained with Trypan blue at different times of study at room temperature, and the viability of adipose cells under the microscope was compared. The results of the study were analyzed using SPSS software version 20.</p> Results <p>A total of 15 patients participated in this study, of which 93.3% were women. The mean age of the patients was 40.73 ± 10.42 years. The procedure performed in the majority of patients (66.66%) was abdominoplasty, which was generally performed for cosmetic purposes. The highest viability of adipocytes was observed (about 95%) 30&#xa0;min after harvest. The results showed a clear decrease in the percentage of viable adipocytes over time, especially 2&#xa0;h after harvest. Also, the viability of cells 4&#xa0;h after harvest was 11%.</p> Conclusions <p>The results of the present study indicate that the viability rate of adipocytes decreases with time, and this should be considered by plastic surgeons to select the best time for autologous fat grafting.</p> Level of Evidence <p> Level III, risk / prognostic study.</p>