114 soil samples, 0.0-0.25 m horizon, collected on the Península de Nicoya, Costa Rica (3,000 Km2) at a mean density of one sample each 25 km2, were analized for variables: pH, P, K, Ca, Zn, Cu, Mn, Fe, Mg, and Al. The samples were processed on an IBM 360/40 computer of the Centro de Informática of the Universidad de Costa Rica. Objective and interpretative maps of the different variables were obtained, beside the statistics of the main groups of soils selected according to their lithological origin. P, K, Zn and Fe show lower concentration patterns in relation to the established critical levels in agriculture, characteristic that should be studied because of possible soil deficiencies. K, Ca, Cu, Mn and Fe display very high concentration patterns in relation to the corresponding critical levels, which should also be investigated in order to know their incidence in plant and animal life. Al attains concentration values generally well below the critical level, although it is important to consider in detail the area sorrounding Sámara and Punta Guiones which shows significantly high values. pH is generally low (< 6.4) on the península and especially in the northern and south-central portions. With this rust study of environmental geochemistry we hope to gain a more complete understanding of regional soil variations which would lead to a study procedure for practical applications in agriculture and soil management.