1 A method of stereotactic dissection followed by fluorimetric assay, has been used to determine the distribution of noradrenaline, dopamine and 5-hydroxytryptamine (5-HT) within the preoptic hypothalamic area of rabbit brain.2 The method involved subdividing the area into a number of thin slices cut with reference to stereotactic co-ordinates. The amine content of each slice was then determined fluorimetrically.3 Noradrenaline was shown to be concentrated (>2.0 mug/g) in two areas within the preoptic hypothalamic area, both of which were adjacent to the mid-saggittal line: the first was close to the preoptic nucleus and the second immediately caudal to the main group of hypothalamic nuclei.4 Dopamine was evenly distributed throughout the preoptic hypothalamic area.5 5-HT was concentrated (>1.6 mug/g) towards the lateral borders of the area, principally in the region which joins the preoptic area to the anterior hypothalamus.6 The relative merits of the stereotactic approach and the histochemical approach are discussed.