Collective flow of nuclear matter probes the dynamics of heavy-ion rea
ctions and can provide information about the nuclear-matter equation o
f state. Ir. particular, the incident-energy dependence of collective
flow may be a sensitive means to deduce the existence of a quark-gluon
plasma phase in the equation of state. Collective-flow measurements f
rom 30 A MeV to 200 A GeV incident energies are briefly reviewed. Prel
iminary results on collective flow from the WA98 experiment at the: CE
RN SPS are presented.