Dopamine, noradrenaline, and serotonin concentrations in human fetal hypothalamus, striatum, and neopallial cortex are rather low with the exception of a high hypothalamic dopamine level. The catecholamine fluorescence appears in the hypothalamus during the 10th fetal week, and in the median eminence during the 13th week. On the basis of these observations, it is suggested that the hypothalamic monoaminergic mechanism is present and probably functioning in the human fetal brain.