Combine 1 cup water and 1 cup sugar in a small saucepan. Place over medium-low heat and stir until sugar is dissolved. Remove from heat and set aside, allow to cool for 10 minutes.
Pour 1 cup fresh-squeezed lemon juice into a pitcher. Add sugar/water mixture.
Add remaining 5 cups wat and stir well. Pour over ice and serve, or transfer to refrigerator and allow to chill for several hours before serving. Makes 1/2 gallon of lemonade, and can easily be doubled!