There are described the subgroups of the general symplectic group Γ=GSp(2n, R) over a commutative semilocal ring R, containing the group of symplectic diagonal matrices. For each such subgroup P there is uniquely defined a symplectic D-net a such that Γ(σ)≤p≤N_Γ(σ), where Γ (σ) is the net subgroup in Γ corresponding to σ (cf. RZhMat, 1977, 5A288), and N_Γ(σ) is its normalizer. The quotient group N_Γ × (σ)/Γ(σ) is calculated. There are also considered subgroups in Sp(2n, R). Analogous results for subgroups of the general linear group were obtained earlier in RZhMat, 1978, 9A237.