Cut the avocados in half lengthwise and pry out the pits. Remove the peels and cut the avocados into 1-inch pieces. Mash with a fork.
Cut the tomato into ½-inch pieces. Remove the skin from the onion and cut into ¼-inch pieces. Drain off the liquid from the jalapeño peppers and cut the peppers into ¼-inch pieces.
Combine all the ingredients; mix well.
This is a wonderful topping for potatoes and meat dishes as well as a popular dip for tostadas and raw vegetables.