Preheat the oven to 350 degrees F (175 degrees C).

Cream together sugar and butter in a large bowl until light and fluffy. Beat in eggs one at a time, then stir in vanilla. Sift together flour, cocoa, baking soda, and salt; stir into creamed mixture. Mix in chocolate chips.

Drop spoonfuls of dough onto ungreased cookie sheets.

Bake in the preheated oven for 8 to 9 minutes. Cookies will be soft.

Cool slightly on cookie sheet; remove from sheet onto a wire rack to cool completely.