Introduction: Corticospinal excitability maps obtained with transcranial magnetic stimulation (TMS) are used to assess plasticity of the central nervous system in motor learning and rehabilitation. With conventional methods, a single map usually takes 15-20 min to acquire (1-3). Due to this poor temporal resolution this method is not feasible in a clinical research setting. This study aimed to optimise the method in order to reduce the acquisition time. In addition, we investigated the effect of inter-stimulus interval and stimulation intensity on the map. Methods: TMS was used to elicit motor evoked potentials (MEPs) in first dosal interosseous. Frameless stereotaxy (BrainSight 2, Rogue Research) was used to record the 3D position and orientation of 100 stimuli within a 6 x 6 cm2 area over the hand area of the primary motor cortex. The stimulation positions and EMG records were combined and projected on a 2D plane using an off-line custom written Matlab script. The effect of two parameters on the map were studied: inter stimulus interval (ISI; 1, 1.5, 2, 3 and 4 s) and stimulation intensity (SI; 110%, 120% and 130% of resting motor threshold (rMT)). Maps were characterised by centre of gravity (COG), area (A) and volume (VOL). A repeated measures ANOVA with planned comparisons was used to compare ISIs at 1, 1.5, 2 and 3 s with the control ISI of 4 s. Finally, the minimum number of stimuli was determined by randomly removing stimuli and recalculating the correlation coefficient relative to a full map. The minimum number of stimuli required for a map was determined when the correlation coefficient dropped below 0.9. Results: ISI: No effect for ISI was found with area (p=0.738), volume (p=0.981) or COGx (p=0.648). A significant main effect was found for COGy (p<0.001). However, planned comparisons failed to show any difference for any parameter between 1 s and 4 s (p=0.737), suggesting stimuli could be delivered at 1 s or greater without affecting the map. SI: The map scaled with SI (A: p<0.001; VOL: p< 0.001). A Bonferroni post hoc comparison revealed all pairs being different. The minimum number of stimuli to create a reliable map was 51 ± 19. Conclusion: We have shown that maps may be produced an ISI of 1 s, however some operators reported difficulty at the speed, therefore we suggest 1.5 s may be better. At 1.5 s and 120% rMT, a reproducible map may be created with 70 stimuli (mean + 1 SD), i.e. less than 2 min. Maps were less reproducible at 110% rMT due to greater MEP variability. With this significant reduction in acquisition time the method becomes feasible to be used in the clinic and in motor learning studies where greater temporal resolution is required.