Female pheromones (copulins), which are present in vaginal secretions, influence male perception of females and may induce hormonal changes in males. The mutual pheromonal influence between the sexes is discussed as a result of sex-specific reproductive interests which are a consequence of evolutionary constraints.
Title: Battle of odors: significance of pheromones for human reproduction
Author: Grammer K; Jutte A

Female subjects were given a lingerie and instructed to wear it to bed on two consecutive nights. The subjects were also given scentless soap and other toilet articles and told to use them only. At the end of this period all the lingerie were put into boxes and rated by the men on the basis of smell alone. Some boxes were filled with new lingerie to act as controls.
Results: Male subjects preferred the boxes containing lingerie that had been worn by females with dissimilar immune systems as rated by MHC. Many men said that the smells reminded them of old girl-friends, while lingerie worn by women with similar immune systems reminded them of female family members.
Subjects: 44 men and 49 women
Zoologist, Claus Wedekind, Switzerland

A number of studies have been done that seem to indicate that men in public places (movie theatres, restaurants etc.) will choose to sit in seats that have been sprayed with the pheromone Copulins more often than they will choose seats that have not been sprayed.

Another studied showed that men will rate photos of women higher if they are given a whiff of Copulins while they are looking at the photos.

ABC News conducted an informal test of synthetic pheromones in a singles bar, using two sets of identical twins, one male and one female. One member of each pair was given an unscented pheromone spray while the other was given plain witch hazel containing no pheromones. The subjects were placed in different sections of a popular bar in New York City, and told not to "make the first move". The men received about equal attention from the opposite sex, but the sister who was wearing the pheromones was approached by 30 men as compared to who her no-pheromones sister with only 11 "hits". Bill Ritter was quoted as saying: "We cannot deny what we saw happen in the bar."

Apparently, a similar test was performed in a bar in Germany using hidden cameras and identical twin sisters wearing identical dresses. Again, one sister used pheromones and one did not, and again the sister wearing the suppplements got significantly greater attention from men.