Alternative Splicing Effects ASsessment Tools (AS-EAST) is an online tool for the functional annotation of putative proteins encoded by transcripts generated by alternative splicing (AS). When provided with a transcript sequence, AS-EAST identifies regions altered by AS events in the putative protein sequence encoded by the transcript. Users can evaluate the predicted function of the putative protein by inspecting whether functional domains are included in the altered regions. Moreover, users can infer the loss of inter-molecular interactions in the protein network according to whether the AS events affect interaction residues observed in the 3D structure of the reference isoform. The information obtained from AS-EAST will help to design experimental analyses for the functional significance of novel splice isoforms.