Three kinds of physically cross-linked syndiotacticity-rich poly(vinyl alcohol) (s-PVA) hydrogels were prepared at 0 degrees C with use of the buffer solutions (BS) of pHs 4.0, 7.4, and 9.0. Three gels swelled at first and then began to shrink after 12 h when they were dipped in the same BS for preparation at higher temperature than 0 degrees C. The release of Brilliant Blue (3 mg/l mt) from the cylindrical gels prepared using BS of pH 7.4 was studied at 27, 37, and 47 degrees C. Brilliant Blue has been released spending 4-12 h almost completely. The rate of release from the gel at temperatures of 27, 37, and 47 degrees C became large with increasing temperature. The main factor on release of Brilliant Blue is not the contraction of gel, but swelling, because the degree of swelling (DS) became large with increasing temperatures for 27, 37, and 47 degrees C. The rate of release from the gel (pH 4.0) was larger than that (pH 7.4) due to the increased DS of the hydrogel in early step at pH of 4.0. The apparent diffusion exponents of these releases at pH 7.4 evaluated from first 60% of the fractional release were lower than 0.45 due to the swelling during release. The exponent at pH 4.0 was 0.45 due to immediate swelling. The on-off of shrinking behavior of atactic PVA (a-PVA) hydrogel was observed under several temperature changes. The rate of release of Brilliant Blue at 5 degrees C was lower than that at 27 degrees C and no change was observed at 5 degrees C after one on-off cycle.