The invention generally relates to golf clubs with adjustable mass properties. In certain aspects, the invention provides methods and mechanisms for adjusting a club head center of gravity and/or moment of inertia by way of an adjustable weight assembly positionable along the sole of the club head body. When in a first position, the weight assembly provides a lower center of gravity so as to increase launch angle and reduce spin rate, resulting in greater overall distance of ball flight. When in a second position, the weight assembly provides a greater mass moment of inertia, which effectively enlarges the sweet spot and produces a more forgiving club for off-center hits.