The following problems are investigated: (1) The existence of well‐behaved ∗︁‐representations on a ∗︁‐algebra 𝒜 equipped with an unbounded m *‐seminorm p , in terms of non‐zero p ‐continuous representable (positive) linear functionals on the domain 𝔇(p ) of p . (2) The existence of well‐behaved ∗︁‐representations of a locally convex ∗︁‐algebra 𝒜, in terms of non‐zero unbounded C *‐seminorms on 𝒜 with domain the ∗︁‐subalgebra 𝒜b generated by the hermitian part of the Allan bounded set 𝒜0 of 𝒜. (3) The existence of faithful well‐behaved ∗︁‐representations of a locally convex ∗︁‐algebra 𝒜, in terms of the so‐called unbounded Gel'fand–Naĭmark C *‐seminorm on 𝒜. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)