1. Neutrophils and platelets interact in vitro through multiple bioche
mical pathways in both directions, resulting in an inhibition or a pot
entiation of their reactivity, depending on, the experimental conditio
ns. 2. Under some conditions, a full stimulation of platelets (aggrega
tion and degranulation) can be induced by neutrophils. The present rev
iew is focused on this aspect for which serine proteinases released fr
om the azurophilic granules of neurtophils activate surrounding platel
ets. 3. The different facets of this process at the cellular and molec
ular levels, are presently depicted and their relevance to the in vivo
situation suggested.