Of the 229 806 new male patients attending venereal disease clinics in England in 1976, 31.9% had recognisable non-specific genital infection (NSGI), which was easily the most common diagnostic category of the sexually transmitted diseases (STDs) and one which had increased more markedly than all the others in the previous 25 years. Many more cases of nongonococcal urethritis (NGU) are concealed under the diagnosis of gonorrhoea, as is clear from the high incidence of post-gonococcal infection following treatment with penicillin. From 44% to 56% of male patients with gonorrhoea can also have non-specific genital infection during the same year. A practical treatment schedule for gonorrhoea which is also effective against simultaneously acquired non-gonococcal urethritis would be of great value.