Lambs weighing an average of 35 ㎏ were housed in metabolism cages to study the effects of bentonite, limestone, and NaHCO₃ at 2% levels and alfalfa hay at a 10% level added to all-concentrate lamb diets. Ruminal and systemic parameters were measured during the. onset of acidosis (phase 1). The effects of these buffering materials (alfalfa omitted) on ration digestibility and mineral retention in addition to the ruminal and systemic parameters were investigated under the same conditions following a 20-day adaptation period (phase 2). Adding buffers or alfalfa hay was effective in maintaining a more normal ruminal pH and in preventing lactate accumulation in the rumen. On the third day (phase 1) of high-concentrate feeding, most animals drastically reduced feed consumption, but lambs fed NaHCO₃ or alfalfa hay consumed the entire rations given on day 3. Urinary lactate generally followed the trend observed in rumen samples, and feeding buffers or alfalfa tended to reduce urinary lactate excretion. Lambs fed NaHCO₃ excreted higher (P$lt;.01) Na at days 2 and 3 and those fed bentonite excreted more (P$lt;.05) Ca than those fed control diet at day 3. Other parameters including water intake, urine volume, ruminal mineral concentrations, blood PCV, and plasma lactate were unaffected by treatment. In phase 2, the dietary buffers did not influence rumen pH, lactate, total VFA, individual VFA molar percentages, or mineral concentrations except K which was lower (P$lt;.01) in lambs fed 2% bentonite. No obvious effects due to buffers were observed on PCV, plasma lactate, or mineral concentrations. NaHCO₃ increased urine pH (P$lt;.01) and urine lactate (P$lt;.05). Lambs fed 2% NaHCO₃ digested. more (P$lt;.05) dry matter, crude protein, nitrogen-free extract, and starch, and 2% limestone increased (P$lt;.05) fiber digestibility. 1Dietary buffers generally reduced percent fecal starch and improved starch digestibility. Distinctive improvement (P$lt;.05) in starch digestibility was obtained by feeding NaHCO₃. Higher (P$lt;.05) Mg retention was obtained by feeding 2% bentonite or NaHCO₃. More (P$lt;.01) Ca was retained by limestone-fed lambs and more (P$lt;.01) Na by NaHCO₃-fed lambs, but percent retention was not different from the control.