  We discuss the dependence of various properties of the star formation rate
(SFR) and efficiency (SFE) in molecular clouds (MCs) on the maximum mass
reached by the clouds, based on a previously-published model for MC and SFR
evolution in which the clouds were assumed to be undergoing global collapse,
and the SFR was controlled by ioniztion feedback. Because the model neglects
various other processes, the results presented are upper limits. We find that
clouds with $\Mmax \lesssim 10^4 \Msun$ end their lives with a mini-burst, at
which the SFR reaches a peak of $\sim 10^4 ~\Msun \Myr^{-1}$, although its time
average is only $\SFRavg \sim \hbox{ a few} \times 10^2 \Msun \Myr^{-1}$. The
corresponding efficiencies are $\SFEmax \lesssim $60\%$ and $\SFEavg \lesssim
$1\%$. For more massive clouds ($\Mmax \gtrsim 10^5 ~ \Msun$), the SFR first
increases and then remains roughly constant for $\sim 10^7$ yr, because the
clouds are influenced by the stellar feedback since earlier in their evolution.
We find that $\SFRavg$ and $\SFEavg$ are well represented by the fits $\SFRavg
\approx 100 (1+\Mmax/2 \times 10^5 ~ \Msun)^{2} ~ \Msun \Myr^{-1}$ and $\SFEavg
\approx 0.024 (\Mmax/10^5 ~ \Msun)^{0.28}$, respectively. The massive model
clouds follow the SFR-dense gas mass relation obtained by Gao \& Solomon for
infrared galaxies, extrapolated down to MCs scales. Low-mass clouds fall above
this relation, in agreement with recent observations. An integration of the
model-predicted $\SFRavg$ over a Galactic GMC mass spectrum yields a realistic
value for the Galactic SFR. Our results reinforce the suggestion that
star-forming GMCs may be in global collapse, and still have low net SFRs and
SFEs, due to the evaporation of most of the cloud material by the feedback from
massive stars.

Solar and Stellar Astrophysics;Astrophysics of Galaxies