The main question is whether chemically induced mood enhancement is (if successful) likely to make us happier, or whether it may rather have detrimental effects on our long-term happiness. This question is divided into three: (i) What effects are mood-enhancing drugs likely to have on the long-term happiness of the person who takes these drugs? (ii) How would these drugs affect the happiness of the immediate environment of the people who take them, e.g. children or spouses? (iii) What effects would a wide-spread use of mood-enhancing drugs have on society as a whole, and how would this affect the long-term happiness of its citizens? My answers to these questions are very tentative, partly because we know too little about what non-hedonic effects these drugs can be expected to have. It is possible that these drugs would have detrimental effects on some determinants of happiness, however, e.g. marriage and friendship, social and physical activity, rational problem-solving and mental effectiveness, political participation and interpersonal trust. But on the other hand, there are also a number of determinants of happiness that might be positively affected by a wide-spread and frequent use of mood-enhancing drugs.