A process for producing middle distillates from feedstocks resulting in whole or in part from renewal sources, characterised in that said process comprises at the least the following steps: a) production of a first paraffinic effluent by the Fischer-Tropsch process from a synthesis gas (CO+H 2), b) hydrotreatment of at least a portion of said first paraffinic effluent from step a), in a mixture with a feedstock from a renewable source selected from oils and greases of vegetable and animal origin, fish oils containing triglycerides and/or fatty acids and products from the conversion of lignocellulosic biomass containing a proportion higher than 80% by weight of free fatty acids, esters and glycerides or mixtures of such feedstocks, in the presence of hydrogen and a hydrotreatment catalyst, at a temperature of between 150 and 450°C, at a pressure of between 1 MPa and 10 MPa, at an hourly space velocity of between 0.1 h -1 and 10 h -1 and in the presence of a total amount of hydrogen mixed with the feedstock such that the hydrogen/feedstock ratio is between 150 and 1500 NI of hydrogen per litre of feedstock, said paraffinic effluent from step a) does not undergo any distillation step before being introduced into the hydrotreatment step b), c) elimination of at least a portion of the water from the effluent from the hydrotreatment step b), d) hydroisomerisation/hydrocracking of the effluent from step c) in the presence of hydrogen and a hydroisomerisation/hydrocracking catalyst comprising 0.05 to 10% by weight and at least one noble metal from group VIII deposited on a silica-alumina support, without any binder, containing an amount of silica of between 1 and 95%, expressed as a percentage by weight, said catalyst having: - a BET specific surface area of 100 to 500 m 2 /g, - a mean diameter of the mesopores of between 3 and 12 nm, - a porous volume of the pores whose diameter is between the mean diameter as defined hereinbefore reduced by 3 nm and the mean diameter as defined hereinbefore increased by 3 nm greater than 40% of the total porous volume, - a total porous volume of between 0.4 and 1.2 ml/g, - a volume of the macropores whose diameter is greater than 50 nm representing between 5 and 60% of the total porous volume, and - a proportion of alkali or alkaline-earth metal compounds of less than 300 ppm by weight, e) distillation of the effluent from the hydroisomerisation/hydrocracking step d) to separate at least a middle distillates fraction. a) production of a first paraffinic effluent by the Fischer-Tropsch process from a synthesis gas (CO+H 2), b) hydrotreatment of at least a portion of said first paraffinic effluent from step a), in a mixture with a feedstock from a renewable source selected from oils and greases of vegetable and animal origin, fish oils containing triglycerides and/or fatty acids and products from the conversion of lignocellulosic biomass containing a proportion higher than 80% by weight of free fatty acids, esters and glycerides or mixtures of such feedstocks, in the presence of hydrogen and a hydrotreatment catalyst, at a temperature of between 150 and 450°C, at a pressure of between 1 MPa and 10 MPa, at an hourly space velocity of between 0.1 h -1 and 10 h -1 and in the presence of a total amount of hydrogen mixed with the feedstock such that the hydrogen/feedstock ratio is between 150 and 1500 NI of hydrogen per litre of feedstock, said paraffinic effluent from step a) does not undergo any distillation step before being introduced into the hydrotreatment step b), c) elimination of at least a portion of the water from the effluent from the hydrotreatment step b), d) hydroisomerisation/hydrocracking of the effluent from step c) in the presence of hydrogen and a hydroisomerisation/hydrocracking catalyst comprising 0.05 to 10% by weight and at least one noble metal from group VIII deposited on a silica-alumina support, without any binder, containing an amount of silica of between 1 and 95%, expressed as a percentage by weight, said catalyst having: - a BET specific surface area of 100 to 500 m 2 /g, - a mean diameter of the mesopores of between 3 and 12 nm, - a porous volume of the pores whose diameter is between the mean diameter as defined hereinbefore reduced by 3 nm and the mean diameter as defined hereinbefore increased by 3 nm greater than 40% of the total porous volume, - a total porous volume of between 0.4 and 1.2 ml/g, - a volume of the macropores whose diameter is greater than 50 nm representing between 5 and 60% of the total porous volume, and - a proportion of alkali or alkaline-earth metal compounds of less than 300 ppm by weight, - a BET specific surface area of 100 to 500 m 2 /g, - a mean diameter of the mesopores of between 3 and 12 nm, - a porous volume of the pores whose diameter is between the mean diameter as defined hereinbefore reduced by 3 nm and the mean diameter as defined hereinbefore increased by 3 nm greater than 40% of the total porous volume, - a total porous volume of between 0.4 and 1.2 ml/g, - a volume of the macropores whose diameter is greater than 50 nm representing between 5 and 60% of the total porous volume, and - a proportion of alkali or alkaline-earth metal compounds of less than 300 ppm by weight, e) distillation of the effluent from the hydroisomerisation/hydrocracking step d) to separate at least a middle distillates fraction.