Now that you know about SPD, I know you're going to find resources to help you through this difficult time. The two books that have helped me the most with my 5 y.o. SPD daughter are Sensational Kids and Growing an In-Sync Child. You may be able to identify what's setting off the tantrums by keeping a notebook for several days, and write down what your son is doing preceding the tantrum. If you find he's doing something sedentary prior to the tantrum, he may need more physical input in bursts throughout the day (heavy lifting, pushing, pulling, jumping). My daughter, 5, was diagnosed in July, and giving her heavy work throughout the day, keeps her on an even keel for the most part. The other day she had surgery to put in ear tubes, so she had a pretty quiet day. After supper she started having some major tantrums, so my husband just scooped her up and started holding her really tight. Even though she was weeping and resisting, he kept holding her tight, and after about two minutes, he could feel all her muscles relax, she stopped crying and suddenly became calm and happy. She just needed extra input to compensate for the day of relaxing. If you get a chance to read the two books, you'll learn lots more about this. Welcome to the site. I'm glad you joined us!