Abstract Paradoxical Sleep (PS) deprivation was effected by instrumental and pharmacological methods in four inbred strains, C57BR, C57BL/6, BALB/c and SEC. Instrumental PS deprivation was achieved by the water tank method for 10–24hr. Chlorimipramine. methyl-naphtyl-aziridine and nialamide were also used to obtain 6–24 hr of PS suppression. Later PS rebound was proportional to the duration of PS deprivation but different among strains. In BALB/c and SEC mice, pharmacological deprivation up to 24 hr did not provoke later PS rebound. A single injection of nialamide suppressed PS for about 24 hr, but was not followed by later PS rebound in any of the strains.