We have recently demonstrated that Luizomyia longipalpis salivary gland homogenates (SGH) inhibited the multiplication of Leishmania promastigotes in vitro. The present work shows that Leishmania amazonensis sensitivity to SGH is correlated to the phase of promastigote in vitro growth and can be decreased by the addition of hemin to the culture medium. The possible relevance of these in vitro results is discussed in relation to the development of Leishmania parasites within their sand fly vectors. (C) 1995 Academic Press, Inc.