To assess the prognosis of peripheral T-cell lymphoma unspecified, we retrospectively analyzed 385 cases fulfilling the criteria defined by the World Health Organization classification. Factors associated with a worse overall survival (OS) in a univariate analysis were age older than 60 years (P = .0002), equal to or more than 2 extranodal sites (P = .0002), lactic dehydrogenase (LDH) value at normal levels or above (P < .0001), performance status (PS) equal to or more than 2 (P ≤ .0001), stage III or higher (P = .0001), and bone marrow involvement (P = .0001). Multivariate analysis showed that age (relative risk, 1.732; 95% CI, 1.300-2.309; P < .0001), PS (relative risk, 1.719; 95% CI, 1.269-2.327, P < .0001), LDH level (relative risk, 1.905; 95% CI, 1.415-2.564; P < .0001), and bone marrow involvement (relative risk, 1.454; 95% CI, 1.045-2.023; P = .026) were factors independently predictive for survival. Using these 4 variables we constructed a new prognostic model that singled out 4 groups at different risk: group 1, no adverse factors, with 5-year and 10-year OS of 62.3% and 54.9%, respectively; group 2, one factor, with a 5-year and 10-year OS of 52.9% and 38.8%, respectively; group 3, 2 factors, with 5-year and 10-year OS of 32.9% and 18.0%, respectively; group 4, 3 or 4 factors, with a 5-year and 10-year OS of 18.3 and 12.6%, respectively (P ≤ .0001; log-rank, 66.79).