The study was conducted to determine mineral concentrations in diets selected by goats grazing a thorn shrubland in a semi-arid region of north Mexico. Three goats (38 ± 1.8 kg BW) fitted with oesophageal cannulae were used to collect monthly extrusa samples from February 1999 to December 2000. Animals were sampled two days each month. Sodium, Ca, Mg, K, Co, Cu, Mn, Zn and Fe, were determined by atomic absorption spectrophotometry. Phosphorus was determined by colorimetry. Data were statistically analyzed by completely randomized design. Macro-mineral concentrations of the forage selected by goats varied between months. Mean concentrations for Na, Ca, P, Mg and K were 5, 8, 3, 3 and 22 g/kg, respectively. Forage concentrations of trace minerals also varied between months. Average concentrations of Co, Cu, Mg, Zn and Fe were 25, 6, 39, 66 and 471 mg/kg, respectively. Results suggest that the concentrations of Ca, P, Mg and K were adequate to meet the requirements of adult range goats for maintenance, pregnancy and lactation. Cobalt, Zn and Fe concentrations also meet the requirements. However, Na, Cu and Mn concentrations in the diet were below requirements. Thus, a supplementation schedule is recommended. The Na and P concentrations should be considered with caution because of the saliva contamination of oesophageal samples.