A compar i son of var ious types of t h r u s t c h a m b e r in jec t i on sys t ems is o u t l i n e d . T h e appl icabi l i ty a n d relat ive m e r i t s of several c o m m o n in jec tor heads a re e m p h a s i z e d . T h e use of dyed -wa te r flow ana lys i s a n d h igh-speed p h o t o g r a p h y in in jec tor h e a d spray research is descr ibed. I t is shown t h a t dye flow p e r m i t s d i s t i nc t i on of t h e " p r o p e l l a n t s " i n t h e spray a n d enab les t h e des igner to t a k e corrective s teps if poor d i s t r i b u t i o n is i nd i ca t ed . M e t h o d s of ana lyz ing drople t size a n d a t o m i z a t i o n r a t e s a re r e viewed a n d c o m p a r e d . T h e cause a n d effect of h y d r a u l i c " f l i p " i n orifice j e t s a re discussed, as a re t h e effects of cav i ta t ion a n d feedback i n t h e h y d r a u l i c s y s t e m .