A unified testing framework is presented for large-dimensional mean vectors of one or several populations which may be non-normal with unequal covariance matrices. Beginning with one-sample case, the construction of tests, underlying assumptions and asymptotic theory, is systematically extended to multi-sample case. Tests are defined in terms of U-statistics-based consistent estimators, and their limits are derived under a few mild assumptions. Accuracy of the tests is shown through simulations. Real data applications, including a five-sample unbalanced MANOVA analysis on count data, are also given. Keyword High-dimensional inference • Behrens-Fisher problem • MANOVA • U-statistics 1 Introduction Let X k = (X k1 ,. .. , X kp) ∼ F, k = 1,. .. , n be iid random vectors, where F denotes a p-variate distribution, with E(X k) = μ ∈ R p and Cov(X k) = ∈ R p× p >0. A hypothesis of foremost interest to be tested in this setup is H 0 : μ = 0 against an appropriate alternative, say H 1 : Not H 0. For an extension to g ≥ 2 samples, let X ik = (X ik1 ,. .. , X ikp) ∼ F i be iid random vectors with E(X ik) = μ i ∈ R p , Cov(X ik