For homogeneous higher gradient elasticity models we discuss frame-indifference and isotropy requirements. To this end, we introduce the notions of local versus global SO(3)-invariance and identify frameindifference (traditionally) with global left SO(3)-invariance and isotropy with global right SO(3)-invariance. For specific restricted representations, the energy may also be local left SO(3)-invariant as well as local right SO(3)-invariant. Then we turn to linear models and consider a consequence of frame-indifference together with isotropy in nonlinear elasticity and apply this joint invariance condition to some specific linear models. The interesting point is the appearance of finite rotations in transformations of a geometrically linear model. It is shown that when starting with a linear model defined already in the infinitesimal symmetric strain ε = sym Grad[u], the new invariance condition is equivalent to isotropy of the linear formulation. Therefore, it may be used also in higher gradient elasticity models for a simple check of isotropy and for extensions to anisotropy. In this respect we consider in more detail variational formulations of the linear indeterminate couple stress model, a new variant of it with symmetric force stresses and general linear gradient elasticity. 3 tr(X) ½ ∈ sl(3) and we have the orthogonal Cartan-decomposition of the Lie-algebra gl(3) gl(3) = {sl(3) ∩ Sym(3)} ⊕ so(3) ⊕ R·½ , X = dev sym X + skew X + 1 3 tr(X) ½ ,(1.1) simply allowing to split every second order tensor uniquely into its trace-free symmetric part, skew-symmetric 2 Indeed, in Murdoch [39, eq.(16)-(20)] we find the same conclusions regarding isotropy of a material point. 3 This remark refers to eq.(1), Mindlin [37], which reads, in the notation of the present paper, ∂ m 31Here, m is the second-order couple stress tensor and σ 21 − σ 12 = 2 axl( skew σ) represents the skew-symmetric part of the total force stress tensor σ. The equation is given for the planar situation, see also eq.(6.11).