In this study we sought to evaluate whether psychological factors in males affect semen quality and pregnancy. In 1076 men of infertile couples, psychological factors, i.e. exposure to acute stress, coping with stress, the WHO (five) Well-Being Index and the Zung's Anxiety Scale Inventory scores were assessed by a questionnaire at the time of semen analysis. Relationships between psychological factors and semen quality (sperm concentration, rapid and progressive motility and normal morphology) were assessed. In 353 men with infertility duration of < or =1.5 years, sperm concentration > or =5 x 10(6) sperm/mL and a female partner with a laparoscopically confirmed tubal patency, we looked prospectively for relations between psychological factors and the occurrence of a natural pregnancy at a 6-month follow-up (n = 124), and first-trimester loss (n = 18). Anxiety trait, found in 19% of men, was related to previous in vitro fertilization/intracytoplasmic sperm injection attempts (p = 0.014), cigarette intake (p = 0.006), alcohol intake (p = 0.026) and sexual difficulties (p < 0.001). Regression analyses indicated a significant positive relationship between the level of sperm concentration and the WHO (five) Well-Being Index score, each successive score number accounting for a 7.3% increase in sperm concentration (p = 0.039), whereas no correlation was found between psychological factors and sperm rapid progressive motility and normal morphology. Poorer coping with stress was related to the occurrence of a first-trimester miscarriage (p = 0.016) in the female partner. Possible depression in males is related to decreased sperm concentration, and poor coping with stress is associated with increased occurrence of early miscarriage.