Gather the ingredients.
Wash the strawberries, and hull them. Discard the caps and stems.
Slice or chop the strawberries, and put them in a medium stainless steel or enamel-lined saucepan. Add the sugar and place the pan over medium-low heat. Bring the mixture to a boil, and then add the lemon juice. Keep the mixture at a steady boil for about 10 to 15 minutes, or until the jam reaches 220 F on a candy thermometer (or 8 F above the boiling point of water at your particular altitude). There are other ways to test for jelling. See below.
Stir the jam frequently, and drag the spoon over the bottom of the pan to make sure it isn’t scorching.
Ladle or funnel into a one-pint jar or container. Cover and refrigerate. Take the jam out to use, and refrigerate as soon as possible after each use for the longest storage time (about 3 weeks).