This is what I found out from the bash docs:

# BASH profiles:
# a) login shell:
#     1. source /etc/profile
#     2. source .bash_profile OR .bash_login OR .profile
#     at logout source .bash_logout
# b) interactive shell:
#    source .bash_rc
# c) non-interactive (PS1 is NOT set!) :
#    if ENV is set THEN source $ENV
#

                  Wolfgang