  Theoretical views on particle acceleration in astrophysical sources and
propagation of cosmic rays (CR) depend very much on the quality of the data,
which become increasingly accurate each year and therefore more constraining.
On the other hand, direct measurements of CR are possible in only one location
on the outskirts of the Milky Way and present only a snapshot of very dynamic
processes. The theoretical papers presented during the conference offer
exciting insights into the physics of cosmic accelerators and processes which
underlie the measured abundances and spectra of CR species.
  This paper is based on a rapporteur talk given at the 28th International
Cosmic Ray Conference held on July 31-August 7, 2003 at Tsukuba. It covers the
sessions OG 1.3 Cosmic ray propagation, OG 1.4 Acceleration of cosmic rays, and
a part of HE 1.2 Theory and simulations (including origins of the knee).
