The present study was carried out to examine whether demecolcine and sucrose affect the formation of a cytoplasmic protrusion containing chromosomes in pig oocytes independently or in combination. In the presence of 20 mM sucrose, the rates of oocytes with a cytoplasmic protrusion after culture for 60 min with 0.2-1.0 microg/ml demecolcine were significantly higher than those with 0.01-0.05 microg/ml demecolcine. When oocytes were cultured for 15 min in the presence of 0.2 microg/ml demecolcine and 20 mM sucrose, 35.1% of them extruded a cytoplasmic protrusion; this rate was significantly lower than those of oocytes cultured for 30-90 min. In the presence of 0.2 microg/ml demecolcine, significantly fewer oocytes extruded a cytoplasmic protrusion after culture for 30 min with 160 mM sucrose than with 0-80 mM sucrose. Significantly more oocytes extruded a cytoplasmic protrusion after culture for 30 min with 0.2 microg/ml demecolcine than without it, regardless of the presence or absence of 20 mM sucrose. In 88.9-100% of the oocytes, the cytoplasmic protrusions contained chromosomes with no significant differences among the different concentrations of demecolcine and sucrose and among the different treatment times. The results of the present study show that the cytoplasmic protrusion containing chromosomes in the pig oocyte is attributable to demecolcine, but sucrose does not affect its formation.