A questionnaire study was carried out to examine the effects of familiarity, ethnicity, sex, age, and social status upon the perception of crowding. Ss were 142 female college students who were required to estimate the maximum number of other people with whom a fictitious person of the same sex and age as the Ss' was expected to share a given room without feeling uncomfortable. All the factors were demonstrated to be significant determinants for the perception of crowding. Personal space was measured with an instruction which told each S to stop at the minimum distance on a tape measure where she did not feel uncomfortable. A hypothesis was supported that there is a significantly negative relationship between crowding and personal space. But correlation coefficients were very low.