In this retrospective study, the authors report the rebound phenomenon after intravitreal triamcinolone acetonide (IVTA) injection for macular oedema secondary to diabetic retinopathy (DR) and central (CRVO) or branch retinal vein occlusion (BRVO). The incidence of a rebound phenomenon was defined as an increase in central retinal thickness (CRT) of greater than 10% from baseline at two months after IVTA injection. The study included 211 consecutive patients (268 eyes); 31% were female and 69% male. The mean (±SD) age was 71.8 ±11.2 years (range 31-94 years); 190 (71.2%), 39 (14.6%) and 39 (14.6%) eyes had macular oedema due to DR, CRVO and BRVO respectively. In total, 9.7% of the eyes showed a rebound phenomenon (DR: 9.5%, CRVO: 5.2%, BRVO: 15.4%). The mean number of prior injections of vascular endothelial growth factor inhibitor or corticosteroid agent was statistically significantly higher in the rebound group (6.8 vs. 5.3) than in the non-rebound group (p=0.01). DR was non-proliferative in 164 (61.4%) eyes and proliferative in 26 (9.7%) eyes. When comparing the non-rebound to the rebound group, no statistically significant difference was found regarding mean age (p=0.28). Females showed a trend towards an increased risk for a rebound phenomenon without reaching significance level (p=0.07). No significant difference was found between the two groups (non-rebound / rebound) at baseline regarding the presence of neurosensory retinal detachment (NSD), vitreoretinal traction (VRT) and epiretinal membrane (ERM) (p=0.24, p=0.38, and p=0.15, respectively). The mean BCVA increased from 20/125 to 20/100 EDTRS letters in the non-rebound group and decreased from 20/125 to 20/160 EDTRS letters in the rebound group (p=0.12). The mean CRT decreased from 527 ±218 to 322 ±184µm in the non-rebound group and increased from 413 ±172 to 525 ±224µm in the rebound group (p=0.20). In the non-rebound group, a weak correlation was found between the reduction of CRT and the improvement in VA (r=0.15, p=0.02), whereas no such correlation was evident in the rebound group (r=0.49, p=0.14). The study concluded that the therapeutic effect of IVTA for macular oedema in DR and RVO can be limited by a rebound phenomenon. It is not a rare phenomenon, however, an increased number of prior intravitreal injections is deemed to be a risk factor. Limitation: Retrospective nature. Strength: Large cohort.