Orthogonal Polarisation Spectral imaging is a new clinical technique that uses polarised light to visualise the microcirculation of organ surfaces. We have used this technique to compare the functional microcirculatory properties of three types of brain tumour with those of the normal cortex. Meningiomas were characterised by chaotic and dilated vessels with almost no erythrocyte movement and a dark background, glioblastoma by few vessels with low flow and a background close to that of the healthy cortex, and metastases by a very dark background, almost no flow, and a chaotic vascular pattern. This technique could provide useful information about microcirculatory morphology and kinetics for diagnostic use during neurosurgery.