A systematic study of the influence of the nature of organic electrolytes on the formation and morphology of the macropores obtained on various medium- and low-doped p-type silicon samples (15-0.015 Omega cm) during anodization is presented. Optimizing the HF/organic solution composition allows extension of the limit of macropore formation to medium- doped p-type Si (rho = 0.1-0.2 Omega cm). The results point out the role of chemistry in the macropore formation process.