Patients enrolled on the bioavailability portion of this study receive one dose of IV penclomedine over 1 hour followed by 2 weeks of rest. At the end of two weeks, they receive oral penclomedine for 5 days every 28 days. The starting dose is determined by a single primary patient who has been administered oral penclomedine and observed for dose limiting toxicity (DLT). [Bioavailability portion completed as of 3/98.] Those not on the bioavailability portion of study start on a standard design dose escalating schedule in which patients enroll in cohorts of 3. Patients are administered oral penclomedine daily for 5 days. This treatment repeats every 4 weeks. The MTD is defined as the dose immediately below that at which 2 patients experience DLT. Treatment repeats for 6 courses or until severe toxicity or tumor progression is observed.