In 19 cases of early seborrheic trichomadesis (alopecia seborrhoides praematura) and in 15 cases of trichophalakrosis (calvities seborrhoides inveterate) the basal cutaneous flow of the scalp – as ascertained by dermal <sup>131</sup>Jodine clearance rate, skin temperature, and thermopill flowmetric recording – is evaluated in comparison with 10 normal controls. High flow values, with uniform and symmetrical distribution, with average rates not significantly different from the normal controls, were generally obtained. In a relatively small percentage of the inveterate cases, a slightly lower flow regimen with a delayed reheating time test, were encountered. Critical and short-time hyperemic responses were elicited by perspiratory (thermal, emotional) or psychical (mental reckoning) stimuli, in subjects with peculiar lability of microcirculatory adjustment of the affected areas. A close correlation between basal flow rate and metabolic intensity of the corresponding scalp fragments confirmed the strict linkage between both histangic factors. Rubbing and hyperemising topical procedures were followed by a small increase of the mean blood flow of the scalp. Following conclusions were drawn: 1. There exists a stabilizing mechanism of the scalp blood flow, with thermoregulatory properties, that undergoes some perturbations only in wide and inveterate stages of hair denudation. 2. Seborrheic alopecic skin areas are often characterized by unbalanced perfusion control against perspiratory and emotional impact situations, but not by a significant reduction of the basic skin flow, that even in severe follicular impairment seems to be largely exceeding the metabolic needs of the tissue. 3. There is a satisfactory linearity between oxydative metabolism and flow of the affected areas. Circulatory changes seem therefore to be secondary to the parenchymatous changes of the hair, in histangic connection therewith. 4. A sound circulatory foundation for the flow-increasing treatment of the scalp (as is today largely used in the therapeutic trial of seborrheic alopecias) does not exist.