Scaffolding provides content-area teachers (CATs) with an effective means to integrate language instruction into content-area instruction for English language learners (ELLs). Data for this study were derived from 33 CAT discussions while they were pursuing professional development in an American university classroom over 32 weeks. The discussions yielded 408 scaffolding statements that were coded and analyzed. The findings identified linguistic, conceptual, social and cultural scaffolding as part of the CATs' personal practical knowledge. Also, the findings demonstrated that CATs' knowledge of cultural scaffolding is limited in comparison to other scaffolding strategies. The findings have an impact on the nature of ELL instruction and its effectiveness. (Contains 1 figure and 4 tables.)