The results of an experimental study on the formation and development of sediment bars in straight and meandering channels, are reported. The laboratory observations are used to analyze recently developed linear and nonlinear theoretical models for the formation, geometrical properties, and migration characteristics of alternate bars. The theoretical predictions are found to be in good agreement with the observations of height, wavelength, and celerity of alternate bars. The theoretical conditions for which the suppression of migrating bars in meandering channels takes place, seem to agree qualitatively well with the experimental observations made in the laboratory.