Preheat oven to 350 degrees. Grease cookie sheets. (I use parchment paper).
In a medium bowl, combine peanut butter and sugar together until smooth. Beat in the eggs, one at a time, then stir in the baking soda and vanilla. Roll dough into 1 inch balls and place them 2 inches apart onto the prepared cookie sheets. Press a criss-cross into the top using the back of a fork.
Bake for 10 minutes in the preheated oven. Allow cookies to cool on baking sheet for 5 minutes before removing to a wire rack to cool completely.
For 36 cookies, each cookie has approx. 115 calories!