Heat shock proteins (Hsps) are conserved molecular chaperones that are upregulated following exposure to environmental stress and during aging. The mechanisms underlying the aging process are only beginning to be understood. The beneficial effects of Hsps on aging revealed in mild stress and overexpression experiments suggest that these proteins are part of an important cell protection system rather than being unspecific molecular chaperones. Among the Hsps families, small Hsps have the greatest influence on aging and the modulation of their expression during aging in Drosophila suggest that they are involved in pathways of longevity determination.