Paraprofessionals are increasingly hired in US schools to support the learning and behavior needs of students with or at risk for disabilities; despite receiving very limited professional development supports to enhance their skills in classrooms. The research base is lacking on effective paraprofessional professional development and intervention provision. This special issue is the first to showcase the current science and knowledge of such practices for paraprofessionals. The six articles included in the special issue offer the range and depth of work in this area. Two articles focus on practices of supervision and assessments for paraprofessionals and one article critically appraises the professional development research for paraprofessionals working with student with challenging behaviors. The final four articles examine the effectiveness of paraprofessional as implementers of interventions in classrooms. The studies in this special series offer insight and ideas on the next generation of paraprofessional research, practice and policy for the field. Finally, the special issue concludes with a commentary synthesizing the current work and offers "big ideas" for future development and validation initiatives. [For the corresponding grantee submission, see ED616967.]