The pathophysiology of ascites in patients with cirrhosis is complex and includes increases in hepatic sinusoidal pressure, the formation of hepatic and splanchnic lymph, renal sodium retention, and hypoalbuminemia. However, the role of hypoalbuminemia in ascites formation is controversial. Evaluating ascites in hypoalbuminemic patients with nephrotic syndrome could add to our understanding of the role of hypoalbuminemia in ascites development. We conducted a retrospective analysis of 52 adults and 21 children with nephrotic syndrome who were hospitalized in the Hadassah University Hospital on Mount Scopus during 1981-1994. There was a significant difference in the prevalence of ascites between pediatric (52%) and adult patients (23%) (p = 0.024). Pediatric patients had lower serum albumin levels than adults (1.70 ± 0.08 g/dl vs. 2.10 ± 0.07 g/dl, p = 0.001). Adult patients with ascites had lower serum albumin levels than adult patients without ascites (1.80 ± 0.13 g/dl vs. 2.20 ± 0.07 g/dl, p = 0.01). This difference was not found in pediatric patients. Temporary fluctuations in liver enzymes (up to four times the upper limit of normal for transaminases) were evident in five patients from the pediatric group with ascites, whereas all pediatric patients without ascites had completely normal liver enzymes (p = 0.035). Among the 12 adult patients with ascites, seven had liver disease (three with cirrhosis and four with amyloidosis), and two had right-sided congestive heart failure. Among the 40 adult patients without ascites, only four had liver disease (amyloidosis). The plasma albumin levels of the patients with amyloidosis without ascites were higher than patients with amyloidosis with ascites (1.90 ± 0.10 g/dl vs. 1.50 ± 0.07 g/dl, p = 0.03). Two patients with nephrotic syndrome and ascites (one without liver disease) had episodes of spontaneous bacterial peritonitis. Ascites in nephrotic syndrome is more common in children than in adults. Although in most pediatric patients ascites formation is probably a common manifestation of the general fluid retention, in most adult patients with nephrotic syndrome ascites can be attributed to both hypoalbuminemia and the presence of liver disease or congestive heart failure, with increased hepatic sinusoidal pressure.