Experimental research results are presented concerning the condensation of the R404A refrigerant in a five-channel multiport, which is fed in parallel and consists of mini-channels with internal diameter d = 0.90 and 3.30 mm. The research was performed in the presence of periodic instabilities generated in a frequency range from 5 to 0.2 Hz. During condensation in the multiport, the impact of instabilities is considerably stronger that in the case of single mini-channels. It was found that the temperature profiles and pressure profiles became deformed in each of the mini-channels of the multiport during the condensation process with the generated instabilities. These deformations decreased the value of heat transfer coefficient h, whose value depends on the diameter d of the multiport mini-channels, vapour quality x and the frequency f of the disturbances generated. (C) 2012 Elsevier Ltd. All rights reserved.