We conducted a cross-sectional study in 10 primary care centres in Catalonia, to determine applicability, acceptability and effectiveness of partner notification cards used by patients diagnosed of a sexually transmitted infection (STI) and to characterise these and their sexual partners. Statutorily notifiable STIs included Chlamydia infection, gonorrhoea, syphilis, human immunodeficiency virus (HIV) infection or other STIs as deemed necessary by the treating physician. Between June 2010 and June 2011, 219 index cases were enrolled, of whom 130 were men (59.4%), 71 of them men who have sex with men (54.6%). Chlamydia infection (41.1%), gonorrhoea (17.8%) and syphilis (16.0%) were the STIs most frequently diagnosed. HIV infection accounted for 4% of cases. A total of 687 sexual partners were reported, and 300 of these were traceable through the notification card (45.7%). Those who did not report traceable contacts were older (mean age: 34 years versus 31 years, p=0.03). The main reason for not distributing the card was anonymous sexual intercourse (38%). Patient referral notification cards can reach a high percentage of sexual partners at risk. However, only few notified sexual partners attended participating health centres. Internet-based partner notification may be considered in order to reach those partners not otherwise traceable.