A discontinuous volume collapse occurs on binding of tetraphenylphosphonium chloride (TPPC) to the anionic polyelectrolyte network poly[2-(acrylamido)-2-methylpropanesulfonic acid] (PAMPS) gel. The amount of TPPC inducing volume collapse decreases with increasing temperature. The TPPC binding to the gel is noncooperative and insensitive to temperature change in spite of the strong hydrophobic interaction of TPPC. The mechanism of the TPPC binding is discussed.