A case-control study of sexually transmitted diseases was carried out in two health units in Gondar town, North-western Ethiopia, between September 1987 and November 1987. A total of 285 cases and 570 controls participated in the study. The peak age range was 15 - 19 yea r s (43.9%) and 20-24 year s (34.6%) for female and mal e case s r es pectively. In con trast to reports from other parts o f Afrj~R, th e male-tofemale ratio was 1.2:1 i n t his s t ud~· . Over 40 [: o f the cases were found in Ke ft pgnn four in whi ch there are predominantly soldiers and pros titu tes. Of 153 mal e cases, only 26.2% were married. Ma rri ed women constituted 33.1% of t he cases. While a further 33 . 3% wprA di.vorc ed womAn. Soldiers, prostitutes and students (28.8 %, 19.7% and 13.3% of the total cases respectively) were identified as high risk groups. The commonest diagnosis was gonorrhea (56.5 X), with further 21.8% of the mixed infections including gonorrhea. Over 40% of the case s admitted to a previous history of STD. A past history of four or more STD inf ection s occurred in 10.9% of the total cases. Casual contact or unknown contact as a source of infection accounted for 50% of the infections rivaling prostitutes who accounted for 52.3% of the contacts. Of the total cases, 54.4% sought a cure from druggists without seeing a health worker . The practice of self-medication was high and did not appear to differ greatly between educated and illiterate groups (P>.lO) . Age at first sexual intercourse of less than 20 y ears was associated with a statistically significant increased risk of STD (OR mh = 3. 6 , P<.'OOl ) . H:l\' in:~ '10 s pOLl s e or living away from marital partner nnel/o r ~ :ln I 11 y were :l~ s oc j ntc el with STD infection (1R f = 2 .3, pC. OO I '~;f d CR I ". 3 , /) premarital sex was found to jn~ r rR~e t.h p ri s k of acquiring STD 4.8 times . Hot h the practice of multiple partner within on week and o ne year ]l period were also associated with an increased risk or ~~'1uir i nf': STD (OR f : 13, P<.OOI tnt CHId OR tnh .. = 9.7 P<. 001, !tc. ~I_',,-c .tl\'c.eyl . This study has implications for the control of sexually transmitted diseases in general and AIDS in particular