A large variation of platelet serotonin content over short time interv
als has been shown. This oscillation of platelet serotonin does not re
sult from the accumulation of random technical variations, but can be
considered as an objectively existing phenomenon which might be due to
alternation of serotonin release and uptake processes in platelet-ric
h plasma. Sex and age do not influence the variation of platelet serot
onin.