Capsaicin is the ingredient found in many types of peppers corresponding to the genus Capsicum that make them spicy hot. In addition to that, capsaicin is used as an analgesic and to treat different medical conditions. Capsaicin is a lipophilic molecule and hence its incorporation to membranes should be expected. We have studied the effects of adding capsaicin to model membranes . It was observed by using 2H-RMN that capsaicin increased the fluidity of DPPC model membranes decreasing the onset of the gel to fluid phase transition. For example, at a DPPC/capsaicin molar ratio of 7:1 a spectrum indicating fluid phase appeared at 34ºC and when the molar ratio was 3:1 fluid phase was already present at 28ºC. M1 spectral moments were calculated to better discern the onset of the phase transition revealing that at a 3:1 molar ratio the transition onset was located at 20ºC. The progressive fluidification introduced by capsaicin was also confirmed by 31P-NMR, showing that CSA for a sample with a DPPC/capsaicin molar ratio 19:1 a 26ºC was 63 ppm and it decreased to 52 ppm when the molar ratio was 7:1 and to only 42 ppm if the molar ratio was 3:1. X-ray diffraction was also employed; SAXD showed that the incorporation of capsaicin to give a DPPC/capsaicin molar ratio of 19:1 considerably widened the d-repeating distance at 15ºC going to 73.5 Å to be compared with 65.4 Å in pure DPPC and this d-repeating distance furtherly increased to 75.6 at a molar ratio of 3:1. Lamellar structures were observed at all molar ratios and temperatures studied, but WAXD indicated that already at a molar ratio of 19:1, Lβ structures were present instead of Lβ´as in pure DPPC at 15ºC, i.e. below Tc. Funded by MINECO (Madrid, Spain)[BFU2011-22828] and co-financed by FEDER (European Union).