Novel alkyl diethers of prostaglandins of the formula; ##STR1## wherein R1 is hydrogen or lower alkyl; R2 and R6 are hydrogen when Y is a single bond and R2 and R6 are absent when Y is a double bond; R3 is keto, ##STR2## R'9 is hydrogen or lower alkyl; R'10 is lower alkyl; R'11 is lower alkyl; Z1 is cis or trans --CH???CH-- or --CH2 CH2 --; Z2 is trans --CH???CH-- or --CH2 CH2 --; X is a single bo