NOVELTY - Process (P1) for preparing of crystalline form I of atorvastatin hemi-calcium, comprises adding an aqueous solution of atorvastatin sodium to an aqueous solution of calcium acetate seeded with crystalline form I of atorvastatin hemi-calcium.    USE - The process is useful for preparing crystalline form I of atorvastatin hemi-calcium, which is useful in a composition (all claimed) for treating hypercholesterolemia. No biological data given.    ADVANTAGE - The process: does not uses the organic solvent, hence it is cost effective and eco friendly as compared to conventional processes; and provides the crystalline form I of atorvastatin hemi-calcium with improved purity.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) a process (P2) for preparing crystalline form I of atorvastatin hemi-calcium, comprising: (a) mixing calcium acetate in water; (b) raising the temperature of the obtained mixture to 40-75 degrees C; (c) seeding the mixture of step (b) with form I of atorvastatin hemi-calcium; (d) adding an aqueous solution of atorvastatin sodium to the mixture of step (c); (e) stirring the reaction mixture of step (d) for 30 minutes; (f) cooling the reaction mixture to 0-35 degrees C; (g) stirring the cooled reaction mixture of step (f) for 1-3 hours; and (h) recovering the precipitated form I of atorvastatin hemi-calcium;    (2) a process (P3) for preparing crystalline form I of atorvastatin hemi-calcium, comprising: (a1) dissolving (4R-cis)-1,1-dimethylethyl-6-(2-(2-(4-fluorophenyl)-5-(1-methylethyl)-3-phenyl-4-((phenylamino)-carbonyl)-1H-pyrrollyl)ethyl)-2,2-dimethyl-1,3-dioxane-4-acetate in acetonitrile; (b1) raising the temperature of the obtained reaction mixture to 30-70 degrees C; (c1) cooling the mixture of step (b1) to 0-30 degrees C; (d1) adding dilute hydrochloric acid to the reaction mixture of step (c1) drop wise; (e1) stirring the reaction mixture of step (d1) for 1-3 hours; (f1) adding aqueous solution of sodium hydroxide to the reaction mixture of step (e1); (g1) raising the temperature of the reaction mixture of step (f1) to 30-70 degrees C; (h1) stirring the reaction mixture of step (g1) for 1-3 hour; (i1) removing the solvent from the reaction mixture of step (h1); (j1) charging methanol to the reaction mixture of step (i1); (k1) stirring the reaction mixture of step (j1) for 15-50 minutes at a temperature below 45 degrees C; (l1) removing the solvent from the reaction mixture of step (k1); (m1) charging tert-butyl methyl ether to the reaction mixture of step (l1); (n1) stirring the reaction mixture of step (m1) for 10-30 minutes; (o1) settling the reaction mixture of step (n1) for 1 hour; (p1) separating the lower aqueous layer from the reaction mixture of step (o1); (q1) adjusting pH of the reaction mixture of step (p1) to 8.8-9.2 by adding dilute hydrochloric acid; (r1) adding the reaction mixture of step (q1) to aqueous calcium acetate solution seeded with form-I of atorvastatin hemi-calcium; (s1) stirring the reaction mixture of step (r1) for 10-60 minutes; (t1) cooling the reaction mixture of step (s1) to 0-30 degrees C; (u1) stirring the cooled reaction mixture of step (t1) for 1-3 hours; and (v1) recovering the precipitated form I of atorvastatin hemi-calcium; and    (3) a pure crystalline form I of atorvastatin hemi-calcium prepared by the process (P2) or (P3).