This study validated a measure of pregnancy planning effort based on Miller's conceptual framework in two clinical settings. The questionnaire's main items deal with general behaviour with regard to pregnancy, timing and proception (proception being the reverse of contraception). Values for these three items are added to yield a continuous score ranging from 0 to 12. The study population comprised 448 women of different cultural backgrounds recruited in prenatal, fertility and family planning clinics in Quebec and North Carolina. The results indicate that the internal consistency between the three items pertaining to pregnancy planning was excellent (Cronbach's alpha of 0.83). Test-retest reliability after a 4-week interval was excellent, with an intraclass correlation coefficient of 0.86 for the planning score. The planning score median for women attending family planning clinics (1.00) was significantly lower than that for those recruited in fertility clinics (11.00), confirming the discriminant ability of the instrument. Path analysis shows that the conceptual model corroborates the observed data and explains 53% of the pregnancy planning variability. In conclusion, this is the first questionnaire specifically designed to assess the intensity of pregnancy planning effort, a potentially important variable in epidemiological studies and clinical practice.