Low organic matter and low available moisture supplying soils in southern Illinois lend themselves to no-tillage crop production, but concern about compaction and rooting depth have led some to employ the use of periodic tillage.  A field study was conducted at two locations in southern Illinois between 2000 and 2006 to evaluate the effects of periodic deep tillage (ripping 40-45 cm with minimum surface disturbance style shanks) prior to corn or soybean production. Deep tillage occurring either every year, every other year or every fourth year was compared to continuous no-tillage and continuous chisel tillage systems. Corn and soybean were grown annually and rotated between two fields at each location. Locations included the University of Illinois Dixon Springs Agricultural Center (DS) and Brownstown Agronomy Research Center (BR). Each tillage treatment listed above was split with two secondary tillage treatments (no-tillage versus disk /field cultivator tillage). Because of the rough surface of the chisel treatment, secondary tillage treatments consisted of minimum tillage (single disking) versus disk/field cultivator tillage. For the most part, continuous no-tillage produced the highest yields. Tillage such as chisel tillage or disk tillage reduced the surface residue which probably led to reduced soil moisture availability during times of moisture stress. There is no indication from this study that the periodic tillage of no-tillage systems would justify the fuel and equipments costs.