Magnetoresistive properties of La1-xSrxMnO3-delta (x = 0.15-0.30) bulk polycrystalline samples sintered at temperatures T-S = 1300-1360 degrees C have been investigated. As T-S decreases, the low-temperature magnetoresistance has been found to increase, the effect reaching its maximum value at x = 0.20. (C) 1999 Elsevier Science B.V. All rights reserved.