I have been experiencing smelly flatulence. What could be wrong?

Rarely serious. Although foul smelling or excessive flatulence is often a source of embarrassment, it is rarely associated with serious illness. Offensive odor, when present, is most often due to dietary factors and may be due to sulfur-containing compounds, such as methanethiol, dimethyl sulfide, and hydrogen sulfide, as well as short-chain fatty acids, skatoles, indoles, volatile amines, and ammonia.