In semi-arid Morocco and Spain, increasing concerns about soil and environment quality degradation have raised the need to review existing tillage management systems and develop new systems for seed-bed preparation. Water shortage is accentuated with soil quality depletion and conditions of stress are exaggerated under present land uses. Research on tillage management systems started early 1980s in semiarid Morocco and early 1990s in Spain in order to propose to farmers the best options for managing soils and crops. The No-Tillage (NT) system was found to boost production vis-à-vis the erratic climate of semiarid Morocco. In semi-arid Spain, crop development and yield was increased under Reduced Tillage (RT), especially in years with low rainfall. The soil's attributes have drastically changed due to elimination of soil manipulation with tillage tools. The results obtained showed that NT has a positive effect on the indicators of soil quality. Indeed, NT increased the levels of Soil Organic Carbon (SOC), of available P and exchangeable K, and decreased pH. These improvements were significant in top surface (0-25 mm) for the fourth year and did not exceed 0-50mm after six years of experimentation. In semiarid Spain, increases in SOC and nutrient contents were also observed under RT. After a 7-year period, SOC at 0-500 mm was 1.07 % under RT and 0.86 % under CT (with mouldboard ploughing at 300 mm depth and burning the straw of the preceding crop). In Morocco, it was showed increases in SOC of 13.6% with NT, and 3.3% with Conventional Tillage (CT) over an 11-year period, with differences being greater in the top 25 mm layer. Generally, there is a trend towards a stratification of SOC at the surface under NT, without any effect on lower horizons. At 0-25 mm, SOC increased from 5.6 to 7.2 Mg ha-1 under NT, after 4 and 11 years. At the same horizon, SOC level did not change under CT after the same periods. It is also reported that NT soil has sequestered 3.5 and 3.4 Mg ha-1 of SOC more than CT in the 0-200 mm horizon, after 4 and 11 years, respectively. In semiarid Spain, RT soil has sequestered 2 Mg ha-1 of SOC more than CT in the 0-500 mm horizon, after 10 years. Values of stratification ratio of SOC (calculated from SOC in the 0-50 and 50-100 mm soil layers divided by that in the 250-400 mm) under RT were higher than 2, showing the lower level of degradation of this soil with respect to soil under CT. NT affected also organic matter content of aggregates in all classes of a Calcixeroll soil in Morocco. With depth, there is no reduction in these indicators comparing NT to CT. The management of residues showed that in general, the improvement of these indicators was proportional to residue level under NT. These indicators were ameliorated by addition of crop residues and decreased when the soil was left bare. The improvement of C and N is mainly due to the improvement of their particulate fractions, which were found more sensitive to the management of soil and crops. In addition to organic matter, another important related soil quality benefit of continuous NT is the improved aggregation. It is also important to note the significant increases of the Microbial Biomass Carbon (MBC) and some enzymatic activities recorded in soils under RT in semiarid Spain, after a 13-year period. These increases were especially noticeable at the 0-50 mm layer, and could be related to the increase observed for the soluble SOC (326 mg kg-1 under RT and 241 mg kg-1 under CT); correlations between soluble SOC and MBC, and soluble SOC and enzymatic activities were highly significant: r = 0.794, p < 0.01 for MBC; r = 0.918, p < 0.01 for dehydrogenase; r = 0.638, p < 0.01 for alkaline phosphatase; r = 0.864, p < 0.01 for ß-glucosidase and r = 0.908, p < 0.01 for protease. Improvement of these variables indicates that conservation tillage (RT) improves soil quality under rainfed agriculture in semiarid Spain. It is clear from the experiences in semi-arid Morocco and Spain that reduction of tillage or its elimination contributed to quality regeneration of soil attributes.