The effects on visual attention in 4-month-olds of rising, falling, and bell-shaped frequency sweeps taken from natural, infant-directed (ID), female speech were investigated in a habituation-dishabituation paradigm. In both experiments, a checkerboard pattern was presented for 10 s on each of 12 trials, with a 10-s series of five brief sweeps occuring simultaneously with the visual stimulus on the ninth trial. In Experiment 1, infants exhibited renewed visual attention when rising and bell-shaped, but not falling, frequency sweeps were presented. Renewed attention also occured on the subsequent (10th) trial in which the check pattern was again presented alone. However, this Thompson-Spencer dishabituation effect occured only following the rising sweep. In Experiment 2, visual attention increased significantly during presentations of both the rising and falling sweeps, and Thompson-Spencer dishabituation was again observed only following the rising sweep. Synthetic sweep stimuli modeled on the fundamental frequency (F 0) of the rising sweep similarly increased gaze duration but produced no Thompson-Spencer dishabituation. Results are discussed in terms of the attention-controlling and arousing properties of ID frequency-modulated sweeps.