Product-by-product input-output structure models are well suited for specific analytical purposes, such as productivity, cost structure comparison, etc. These models show analytically the economic structure and the relations of sectors with each other in a national economy. In this study, input-output relations between agricultural and other sectors of national economy containing 64, 97 and 59 sectors, respectively, for 1990, 1998 and 2002, were analyzed on the data published by Turk Stat (Turkish Statistical Institute), in order to determine cost (input) structure of the production and backward - forward dependency of the sector. The analysis revealed that agricultural activities have the largest production and supply values among other activity groups in the national economy, even though the shares in GDP are decreased. Besides second biggest gross value added figures were created by agriculture closely after "Real estate activities (Code: 70)" in the economy. These results move the sector in a prominent position in the national economy. "Mechanization Tools & Services" have the first position between outer suppliers with shares fluctuated between 13 and 16% for the duration. "Fuel & Oil" composed big portion of the group and constituted one of the biggest input items alone following "Agricultural Products & Services" together with "Fertilizers & Chemicals" and "Finance" groups. Its shares in total inputs were 13% at 1990 and 1998, but dramatically decreased to 7% in 2002; it should be resulting from the crisis most probably. On the contrary, "Machinery & Equipment" section of this group was well increased from 3 to 6% between 1990 and 1998 and could keep this rate in spite of the crisis in 2002. As a result, it is well understood that mechanization related products & services are most important cost fraction of the agricultural production in Turkey. Farmers spent money amounted to 1,126,163 (Billion TL) and 1,052,083 (Billion TL) for "Fuel & Oil" and "Machinery & Equipment" in 2002, soon after a big crisis affected national economy deeply. The shares of the outer sectors are decreased for the total inputs comparing with the direct inputs. Additionally, the total inputs required from energy related sectors have gain more importance than the direct inputs considered only. Regarding to 2002, agriculture has fewer "Back Dependence Coefficient" compared to other sectors; it is supported by mostly itself. The rank was 46 among 59 sectors. On the other hand, agriculture has one of the highest forward dependence coefficient compared to other sectors; it transfers most of its products to other sectors.