  Despite compelling evidence that stellar bars drive gas into the inner 1--2
kpc or circumnuclear (CN) region of galaxies, there are few large, high
resolution studies of the CN molecular gas and star formation (SF). We study a
sample of local barred non-starbursts and starbursts with high-resolution CO,
optical, Ha, RC, Br-gamma, and HST data, and find the following. (1) The inner
kpc of bars differs markedly the outer disk and hosts molecular gas surface
densities Sigma-gas-m of 500-3500 Msun pc-2, gas mass fractions of 10--30 %,
and epicyclic frequencies of several 100--1000 km s-1 kpc-1.Consequently,
gravitational instabilities can only set in at high gas densities and grow on a
short timescale (few Myr). This high density, short timescale, `burst' mode may
explain why powerful starbursts tend to be in the CN region of galaxies. (2) We
suggest that the variety in CO morphologies is due to different stages of
bar-driven inflow. At late stages, most of the CN gas is inside the outer inner
Lindblad resonance (OILR), and has predominantly circular motions. Across the
sample, we find bar pattern speeds with upper limits of 43 to 115 km s-1 kpc-1
and OILR radii of > 500 pc. (3) Barred starbursts and non-starbursts have CN
SFRs of 3--11 and 0.1--2 Msun yr-1, despite similar CN gas mass. Sigma-gas-m in
the starbursts is larger (1000--3500 Msun pc-2) and close to the Toomre
critical density over a large region. (4) Molecular gas makes up 10%--30% of
the CN dynamical mass (6--30 x 10^9 Msun).In the starbursts, it fuels CN SFRs
of 3--11 Msun yr-1, building young, massive, high V/sigma components. We
present evidence for such a pseudo-bulge in NGC 3351. Implications for secular
evolution along the Hubble sequence are discussed.
