Abstract: The present invention provides pharmaceutical compositions which include (−)-pseudoephedrine and a pharmaceutically acceptable carrier, wherein the (−)-pseudoephedrine is substantially-free of (+)-pseudoephedrine. In another embodiment, the present invention provides methods of relieving nasal and bronchial congestion and of inducing pupil dilation which include administering a pharmaceutically effective amount of (−)-pseudoephedrine to a mammal. The (−)-pseudoephedrine used in the present methods is substantially free of (+)-pseudoephedrine and also substantially free of side effects caused by administration of (+)-pseudoephedrine.