<i>Background:</i> To investigate acute stage (<5 days) evolution of the watershed infarction (WI) on diffusion-weighted (DW) magnetic resonance (MR) imaging and to evaluate the role of perfusion MR imaging in predicting the progression of watershed infarction. <i>Methods:</i> Twenty-eight patients with acute WI within 24 h after symptom onset were selected for this study. Criterion for WI was based on DW images. We assessed the infarct volume changes between the initial and follow-up (mean: 2.2 days) DW images. Perfusion images were obtained in 20 patients at the initial work-up and sensitivity, specificity, and accuracy of perfusion-diffusion mismatch in predicting severe infarct progression were evaluated. Clinical outcome was assessed by using National Institutes of Health Stroke Scale (NIHSS) and modified Rankin Scale (mRS). <i>Results:</i> Infarct volumes on initial and follow-up DW images were 8.6 ± 7.7 cm³ and 20.2 ± 27.0 cm³, respectively. Twenty-one cases showed no or slight increment (<15 cm³) of infarct volume on follow-up MR imaging and seven cases showed severe progression (>15 cm³ increment). Among 20 cases in which perfusion maps were obtained, 5 cases showed perfusion-diffusion mismatch: among those, 4 developed severe progression of infarction. Severe progression group showed higher follow-up NIHSS score and poor outcome by 90-day mRS score. <i>Conclusion:</i> WI usually begins as a small volume lesion, and progression of infarction during the acute stage is usually limited in most cases. Perfusion imaging may have an important role in predicting severe infarct progression in WI.