In 1964, Sweet described an acute febrile neutrophilic dermatosis. It is now widely accepted that Sweet's syndrome belongs to a group of associated neutrophilic dermatoses. Although clinically dissimilar, Sweet's syndrome, pyoderma gangrenosum, subcorneal pustular dermatosis, erythema elevatum diutinum, and a few other conditions can be considered a part of this same pathologic spectrum of inflammatory disorders because of (1) the existence of transitional and overlap forms; (2) the similar histopathologic feature of an infiltrate by normal polymorphonuclear leukocytes; (3) the possible occurrence of extracutaneous neutrophilic infiltrates, defining the neutrophilic disease; and (4) the frequent association with systemic diseases. According to the localization of the neutrophilic infiltrate, we describe neutrophilic dermatoses en plaques (dermal), superficial (epidermal), and deep (dermal and hypodermal). Almost every organ of the body may be involved by a neutrophilic aseptic inflammation. The main systemic diseases associated with neutrophlic dermatoses are hematologic, gastrointestinal, and rheumatologic diseases. Although the pathophysiology of these conditions is still poorly understood, treatment with systemic anti-inflammatory agents is usually efficacious.