We recently established an ERISA 403B plan. We also have a 401-K plan. My question is this: Do contributions to the 403b by HCE need to be considered in 401K ADP/ACP testing? We have HCE's contributing to both plans, receiving a company match in the 401K up to the company limit for match and then contributing additional pretax contributions to the 403b to reach their annual limits of $16,500 plus $5,500 catch-up if eligible.

No, contributions by HCEs to the 403(b) plan will not be included in the 401(k) / 401(m) testing done on the 401(k) plan.

You do have to coordinate both contributions when applying the 402(g) limit on elective deferrals ($16,500 in 2009 for non-catch-up eligible employees), but you seem to be aware of that already.