Observational data on mass-transfer rates and radii of disks indicate that the outer parts of disks in novae and nova-like binaries are sufficiently hot for stationary accretion; those in dwarf novae are too cool to avoid an accretion instability, while these in Z Cam systems are the borderline cases. The mass ratios of novae and nova-like binaries with main-sequence secondaries appear — at a given orbital period — to be systematically larger than those of dwarf novae, implying that higher mass ratios are responsible for higher mass-transfer rates.