This is a mosaic description of PDP-6 LISP, intended for readers familiar with the LISP 1.5 Programmer's Manual or who have used LISP on some other computer. Some of the newer features (e.g. the display) are experimental and subject to change; in such respects this should not be regarded as a final document. Some Distinctive characteristics: Top-level type in is to EVAL. There is no EVALQUOTE. EQUAL will not correctly compare fixed-point numbers to floating-point. Also (ZEROP 0.0) is NIL. T and NIL evaluate to T and NIL. There are not *T* and F. Interpreted variables, and variable used free in compiled functions, are automatically SPECIAL and may be used without restriction to communicate values. Also any PROG and LAMBDA variables in a compiled function may be declared SPECIAL, and will be bound and restored correctly. COMMON does not exist. Flags are not allowed; elements on a property list of an atom are expected to be paired. MAP, MAPCAR, etc. assume the first argument is the function, and the second is the list. Defining of functions is usually done with DEFPROP.