AbstractTransient electric dichroism has been measured for the ferriheme–poly(L‐lysine)[(Lys)n], ferroheme–(Lys)n, and ferroheme–(Lys)n–carbon monoxide (CO) solutions at pH 9–12. The Soret absorption maximum in electronic spectrum (λ), the reduced linear dichroism (ρ∞) at complete orientation and the calculated angle (ϕ) between the porphyrin plane of a bound heme and the oriented polymer axis are determined for the following complexes: a ferriheme–(Lys)ncomplex at pH 9.5–10.5 (λ = 420 nm, ρ∞= 0.50, and ϕ = 19°), a ferroheme–(Lys)ncomplex at pH 9.5–10.2 (λ = 432 nm, ρ∞= 0.77, and ϕ = 0°), and a ferroheme–(Lys)n–CO complex at pH 9.25 (λ = 430 nm, ρ∞= 0.38, and ϕ = 24°). Based on the above data, the validity of the structures of heme–(Lys)ncomple