Rosacea is a benign, chronic, inflammatory disease, affecting mainly the face of people with Fitzpatrick’s skin phototype I, II, and III. It is manifested by episodes of facial erythema, known as «flushings», or by permanent erythema, telangiectasias, papules and pustules, whereas in male patients phymatous hyperplasia of the skin of the nose or other areas of the face may eventually appear. Ophthalmic involvement is not unusual. The disease is generally asymptomatic or may be accompanied by stinging sensation and skin dryness. Recurrences or simple episodes of «flushing» are induced by certain factors including the UV sun radiation. The aetiology and pathogenesis have not been clearly understood so far. Genetic predisposition has been recently considered. Objective The purpose of this study is a contribution to the understanding of the pathogenesis of rosacea. In addition to the histological examination, we organized an extended immunohistochemical investigation, as we knew that this field was almost unexplored by the time our investigation began. Material and methods Sixty nine (69) non-selected patients, i.e. forty four (44) female and twenty five (25) male, were enrolled in the study. Their age range was 20-79 years and the distribution of their «Fitzpatrick’s skin phototype» was as follows: I/25, II/38 and III/6. During the first examination, the duration of disease ranged between 1 month and 15 years, with mean duration 4,1 years. Facial erythema, «flushing» and variable degree of telangiectasias characterized the vast majority, whereas 47 had variable number of papules, 30 had pustules and 5 (all male) had rhinophyma. After each patient was clinically examined, a properly formed questionary was filled. Thereafter, a 4mm punch was used for sampling affected skin. In 9 cases «normal» skin was sampled too. Histological examination was followed by immunohistochemistry. Nine (9) immunohistochemical parameters were chosen for the investigation : the count of CD(4+)T and CD(8+) T-lymphocytes, the count of the epidermal CD1α Langerhans cells, CD68 macrophages and mast cells as well as the expression of VEGF, b-FGF, ICAM-1 and HSP70. These parameters were studied in correlation to the estimated intensity of inflammatory infiltrate (only the groups of high and low intensity were examined), the presence or absence of granulomas, the intensity of the presence of D folliculorum and the degree of solar elastosis (only the groups of high and low degree were examined). Few of these parameters were also correlated to the duration of the disease. VEGF and b-FGF were correlated to the mean vascular density (MVD), a morphometric parameter representative of neoangiogenesis. Finally, a selected number of them was cross-matched. A group of these correlations was statistically based on T distribution (t-test) and another group on the χ2 distribution ( χ2-test). Occasionally, the procedure of Mann - Whitney and Pearson’s coefficient were used. In general, the statistical significance was defined at the level of 0.05 (P=0.05). ................