Both nuclear and cytoplasmic areas are parameters known to be of significance in the diagnosis of malignancy. However, few studies have assessed the effect of fixation on exfoliative cytology and none has looked at such influences upon oral smears. Hence the method of fixation may influence directly diagnostic cytology. The effect of three methods of fixation upon the nuclear and cytoplasmic areas of cells removed from the buccal mucosa was quantitatively assessed. The three methods employed, prior to Papanicolaou staining, were: direct immersion in diethylether and ethanol (1:1 v/v), spray fixation (Vale Smear Fix) and air drying. Three smears from each of 21 patients were used, each slide being allocated randomly a method of fixation. After 24 h all smears were processed for Papanicolaou's stain. The nuclear and cytoplasmic areas were calculated using semi-automated image analysis. No significant differences were found in the two areas whichever method of fixation was used.