  Event-by-event fluctuations and correlations between particles produced in
relativistic nuclear collisions are studied. The fluctuations in positive,
negative, total and net charge are closely related through correlations. In the
event of a phase transitions to a quark-gluon plasma, fluctuations in total and
net charge can be enhanced and reduced respectively which, however, is very
sensitive to the acceptance and centrality. If the colliding system experiences
strong density fluctuations due, e.g., to droplet formation in a first-order
phase transition, all fluctuations can be enhanced substantially. The
importance of fluctuations and correlations is exemplified by event-by-event
measurement of the multiplicities of $J/\Psi$'s and charged particles since
these observables should anti-correlate in the presence of co-mover or
anomalous absorption.
