Saccharomyces cerevisiae and Acetobacter aceti cells were immobilized by entrapment in Ca-alginate or by adsorption on to preformed cellulose beads and were treated with 0-20% (v/v) ethanol and 0-10% (v/v) acetic acid. At 20% (v/v) ethanol, lethal for free yeast cells, 62-72% of the immobilized cells survived. In 10% (v/v) acetic acid, free and adsorbed Acetobacter aceti cells ceased to grow but 69% of entrapped cells survived. Cells released from the carrier showed an intermediate survival (20-60%).