The ability of the CNS to respond to pertubations through modulation of spinal reflex excitability (SRE) has been shown to be affected by ageing (Mynark & Koceja, 2002). Increased excitability levels have been demonstrated with reduced local temperature in young subjects (Oksa et al. 2000). This modulation could be critical for older individuals who already have impairment in postural control mechanisms (Horak et al. 1989). The purpose of this study is to investigate the sensitivity of the SRE to altered local temperature in both young and older women.Ten young (age 22.3 ± 3.3 years, stature 1.63 ± 0.07 m, body mass 58.4 ± 6.6 kg) and 10 older (age 72.5 ± 3.2 years, stature 1.61 ± 0.07 m, body mass 58.4 ± 9.5 kg) healthy females completed three counterbalanced trials on the same day: a control followed by a cooling and a warming trial. Legs were cooled ≅3°C from control muscle temperature (T_m) or warmed ≅3°C from control T .Local temperature was monitored from the measurement of T_m of the vastus lateralis of the dominant leg using a flexible thermistor. SRE was assessed by measuring the soleus H reflex response with the subjects in a seated position. Progressively increasing stimuli intensity were applied until maximum H and M waves were achieved. Data (mean ± S.D.) were analysed using a two-way (age x condition) repeated measures ANOVA with multiple paired t tests (Bonferroni correction) as a post hoc where appropriate. Alpha level was set at P<0.05.A significant increase in SRE was found with cooling in the young subjects only (H/M, +27.0%, Table 1). Both groups exhibited a similar lengthening of the reflex latency with cooling (Hlat, +6.0% in young and +3.8% in older, Table 1) and shortening with warming (-4.6% in young and -4.9% in older, Table 1). The increase in SRE, with cooling, could imply a compensatory modulation in response to the potentially detrimental delay of the reflex in younger subjects which was not observed in older subjects.