The present invention provides the amino acid of a protein that inhibits cellular apoptosis, herein termed the Survivin protein and nucleic acid molecules that encode Survivin. Based on this disclosure, the present invention provides isolated Survivin protein, isolated Survivin encoding nucleic acid molecules, methods of isolating other members of the Survivin family of proteins, methods for identifying agents that block Survivin mediated inhibition of cellular apoptosis, methods of using agents that block Survivin mediated inhibition or Survivin expression to modulate biological and pathological processes, and methods of assaying Survivin activity.