Abstract In this study, effect of partial alcohol reduction on the sensory modification of red wines was investigated. A Merlot and a Syrah wine were partially dealcoholized using reverse osmosis technique to span a range of three different alcohol contents (14–10%) by grape variety. Preliminary triangle tests indicated the existence of very slight differences between the dealcoholized wines of the study. Therefore, adapted descriptive methodologies had to be used. In a first step, wines were described with a comparative sensory profile by 16 trained panellists on 15 sensory attributes. Then, the same panellists profiled the wines with the TDS technique, which consists in identifying and rating sensations perceived as dominant repeatedly until the perception ends. Analysis of variance of the classical descriptive data confirmed the existence of subtle sensory differences among wines from a given grape variety with only three and five discriminated attributes for Merlot and Syrah, respectively. Analysis of TDS curves emphasized twice more discriminated attributes and pointed up temporal differences between wines that did not appear with the conventional sensory profile. Used together these methods appeared as promising as they resulted in complementary and complete descriptions of wines. Effect of dealcoholization was variable from one grape variety to another one. The constant effects of alcohol reduction, common to both Merlot and Syrah were the perception decrease of heat sensation, the substitution of heat sensation in attack by astringent (Merlot) or red fruits (Syrah) sensations, the decrease of bitter sensation after attack to the expense of fruity sensations, and the decrease of length in mouth. In case of Merlot, texture and astringency sensations were also affected by alcohol reduction whereas for Syrah, sweet sensation was affected. Wine is a complex product lying on a fragile balance and the least parameter modification induces variable effects according to the type of wines. Several kinds of interactions between ethanol and wine component must take place and make difficult the generalization of alcohol reduction effect on the sensory perception of wines.