Painless genital ulcer — chancre; syphilis; benzathine penicillin. STIs: syphilis (Treponema — chancre — painless — → secondary rash — palms/soles → latent → tertiary — gumma, aortitis: benzathine penicillin — single — early; 3 weekly — late), gonorrhea (purulent discharge — dysuria: ceftriaxone + doxycycline — chlamydia cover), chancroid (H. ducreyi — soft painful sore — bubo: azithromycin), LGV (Chlamydia L — bubo — groove sign: doxycycline 21d), donovanosis (beefy ulcer — azithromycin). Treat partners — screen HIV. The painless ulcer is chancre — penicillin cures.