Models for hydration effects that treat the solute and solvent as dielectric continua with different dielectric constants have achieved considerable popularity in recent years. Here we compare such models with microscopic molecular dynamics simulations for a variety of conformational transitions in peptides. The conformational changes studied include changing backbone torsion angles in the alanine dipeptide; formation of hydrogen bonds of the sort seen in antiparallel β-sheets in formamide and alanine dipeptide dimers; transitions from type I to type II β-turns; and propagation of an α-helix from the N- and C-terminal ends. In each case, the peptide solute is described with the CHARMM-19 force field, and continuum solvent models (determined from finite-difference solutions to the Poisson equation and a surface-area term) are compared to free energy simulations using explicit TIP3P water as a solvent. In general, the agreement between the two theoretical methods is good, but “solvation” of a CHARMM-19 solu...