A series of studies since 1908 has established that the reliability of witnesses is strongly influenced by personality factors. The ability of a witness to identify a suspect depends largely on recognition of the individual's face and physical characteristics, but suspects' age and color may also play a role. In addition, identification may be affected by any number of factors, e.g., whether photographs for identification are black and white or colored, the degree of attractiveness of ugliness of the suspect's face, unusual facial expressions or characteristics, and the characteristics of the identifying person. Under stress, men tend to identify suspects more rapidly and accurately. Women tend to be more dependent than men on perceived details within fields. Problems for lineups are similar to those for photos. In some cases, use of videotapes instead of lineups and of two-way mirrors for lineups may help reduce witness stress and improve identification accuracy. Results of a recent study show that witnesses frequently feel under pressure to identify some individual. Removal of this pressure reduces the danger of misidentification. Future research is to focus on the reliability of witness statement, the credibility of witness speaking behavior to judges and prosecutor, and psychological problems of identifying suspects. A bibliography and graphs are supplied.