We have substantially extended the series for the number of self-avoiding w
alks and the mean-square end-to-end distance on the simple cubic lattice. O
ur analysis of the series gives refined estimates for the critical point an
d critical exponents. Our estimates of the exponents gamma and nu are in go
od agreement with recent high-precision Monte Carlo estimates, and also wit
h recent renormalization group estimates. Critical amplitude estimates are
also given. A new, improved rigorous upper bound for the connective constan
t mu < 4.7114 is obtained.