A detailed study is presented of the 0.4–40ncplasma region created by nanosecond, 10.6 mm, 1–38 J laser pulses incident upon unfilled glass microballoon targets. Many interesting features were observed including electron density scale lengths (Lc) and step heights (Np) throughncas short as 0.3l0and as high as 38nc, respectively. An attempt has been made to explain these parameters in terms of recent theories, and a consistent picture only seems to emerge if important roles are assigned to the superthermal plasma component and the effect of inhibited energy transport during laser irradiation.