Background: The existence of 2 distinct forms of psoriasis related to age at onset has been postulated. However, precise data regarding the clinical and epidemiologic characteristics of psoriasis depending on the age at onset are still lacking. Objective: The purpose of this study was to define the clinical and epidemiologic features of this disease in Spain and to compare patients with psoriasis of early and late onset. Methods: An observational, analytic, cross-sectional, multicenter study was carried out. From January 1999 to November 1999, 179 participating dermatologists completed a questionnaire detailing the clinical and epidemiologic features of the first 10 consecutive patients with psoriasis seen in their clinical practice. The sample distribution was proportional to the Spanish population. Both statistical and descriptive analyses were performed. Results: Available data were obtained from 1774 patients. The onset of the disease before 30 years of age was significantly associated with a higher incidence of family history of psoriasis, a more severe and extensive cutaneous involvement, and greater psychosocial impact. Guttate psoriasis, nail involvement, evidence of precipitating factors, and a recurrent clinical course were more frequent in this group of patients. Patients with psoriasis of late onset had a less severe clinical course and a more continuous evolution. Palmoplantar pustulosis was more frequent in this group of patients. No significant relationship was detected between the age at onset and development of joint involvement. Conclusion: Patients with early and late onset psoriasis often show different clinical and evolutionary features. From the analysis of our data, it seems that 2 different groups of patients with psoriasis related to age at onset can be defined. (J Am Acad Dermatol 2002;46:867-73.)