It depends on what kind of mold and where.
If this is just stuff in the shower or bathroom, a solution of 10% bleach (1 part bleach plus 9 parts water) can do the trick nicely. Just make sure to wear good gloves (dish-washing
gloves work fine) and ventilate the room really well. Also, one should wear old clothes because splattered bleach will ruin the color on new clothes.
Answer assisted by David Miller, Medical Student