This study evaluated the clinical, immunological and microbiological results of full-mouth ultrasonic debridement (FMUD) with 10 % povidone iodine (PVPI) as the cooling liquid in the treatment of generalised aggressive periodontitis (GAgP). Twenty-eight patients presenting GAgP were randomly assigned to one of the following groups for evaluation: FMUD + SS (n = 14)-single session of FMUD with 0.9 % saline solution as cooling agent and FMUD + PVPI (n = 14)-single session of FMUD with PVPI solution as cooling agent. Probing depth (PD), relative clinical attachment level (RCAL), relative position of gingival margin, plaque index (FMPI) and bleeding score (FMBS), immunological (interleukin-10 and interleukin-1β concentrations in gingival crevicular fluid) and microbiological (Aa and Pg amounts) parameters were evaluated at baseline, first, third and sixth months after treatment. The two groups presented reduction of FMPI and FMBS and had statistically significant PD reductions, RCAL gains and gingival recession (p < 0.05). Both therapies reduced Pg levels in deep and in moderate pockets (p < 0.05). FMUD + PVPI reduced Aa levels in deep pockets. However, no inter-group differences in clinical, immunological and microbiological parameters were observed (p > 0.05). It could be concluded that 10 % PVPI used as an irrigant solution in FMUD decreased Aa levels in deep pockets but had no additional benefits when compared with saline solution irrigation in terms of clinical, microbiological and immunological results. The FMUD is a valid option for the treatment of GAgP, but the use of 10 % PVPI did not improve the results of the periodontal therapy.20141-150