  This chapter reviews the dynamical processes in young stellar clusters. The
accretion of gas by individual stars affects the dynamics of the cluster, and
the masses of the stars. Dynamical mass segregation cannot explain the degree
of mass segregation observed in clusters such as the Trapezium Cluster in
Orion, implying that the location of the massive stars is an indication of
where they formed. This can, however, be explained by the competitive accretion
model. If most, if not all, stars form in binary systems, then the high
proportion of pre-main sequence binary systems can evolve in clusters to the
smaller proportion of Galactic field stars through binary-binary and
binary-single interactions. These models make definite predictions for the
distribution of binary properties. The early evolution of a cluster sensitively
depends on the primordial binary star proportion. Close encounters between
stars with circum-stellar discs have drastic effects on the discs and on the
stellar orbits. The discs are truncated at radii comparable to the encounter
peri-astron, limiting their lifetimes and affecting their potential for planet
formation. If the gas represents a significant fraction of the total cluster
mass, its removal on dynamical time-scales can unbind the cluster allowing the
stars to escape and populate the field. (shortened)
